The answer to this question will vary greatly depending on your goals and financial capabilities, as well as personal qualities and chosen disciplines.
I will write about my own case. I took the exam back in 2015 in physics and prof. mathematics. On May 9, Foxford opened 24 hours access to all of its courses. Through an extension on Chrome, I downloaded everything that seemed important to me, and reviewed it regularly for the remaining month. (Now, if I'm not mistaken, administrators don't do this anymore :)) There was a similar impression (subjectively everything, of course):
The course "Mathematics, Part C" is very useless (taught by BV Trushin). The teacher spends a lot of time interacting with the chat, waiting. At the same time, an array of problems from the available collections is parsed, the solution to which is already there. It is more efficient to open the problem yourself on reshuege.ru, think for a while, then go through the solution step by step, if you could not master it yourself. By making decisions in this way, a person effectively replenishes the accumulation of experience and improves skills. If it doesn't work at all, then you need to watch video tutorials first, for example, from MIPT on abitu.net, figure out how to approach a particular problem at all.
Better physics at Foxford (Zamyatnin led, a lot depends on the personality of the teacher), but again, there are free alternatives on the sites above.
With regards to motivation and training structure. The money invested in courses does not allow a person to procrastinate forever + the rating system, the calendar of classes does not allow the web to grow in the applicant's head - a positive feature of Foxford. Personally, I logged into reshuege.ru, resolved in the "pass the exam" mode, set myself points for C-shki according to the criteria, and then looked at the statistics and looked at where the indicators were sagging, where not. When a multitude of options began to give an objective picture of problems and successes, I proceeded to specific tasks and solved them - I arranged competitions with myself. In my opinion, this is more interesting than sitting and sticking in books for a year.
If you have certain questions, you can always ask your friends or teachers in the thematic groups of VK - they will help, they will advise free of charge.
P.S. Unified State Exam results: Physics - 100, Mathematics - 84 (adjusted), Russian - 95. P.P.S. In an amicable way, you need to start preparing quietly in the summer after the 10th grade, and it would be nice to study the list of Olympiads from the Ministry of Education and Science, which give benefits, even if you are not too strong in this and have not previously participated (Old for 16-17 years). For example, 1st level can give you automatic admission, 2nd and3rd 100 points in the subject (it all depends on the university and the admission rules). The Phystech Olympiad was a good option for techies. The assignments are acceptable, there are materials from past years, which can be used to prepare, and also the tasks do not go far into the steppe from the exam-shnoy part of S. Good luck))
Courses are usually prepared for a maximum of 85 points. As for the English language, it is most likely even less, because now 40% of all exam scores are written and oral assignments. Here it is obligatory to check and analyze each completed assignment by the teacher, track progress, and an online course cannot give such an opportunity. The same applies to other subjects where there is a part "Composition" - this is the Russian language, social studies.
The quality of classes in Foxford is quite high, it is quite possible to take the course and get a fairly high score on the exam. But if you need a score higher than 85, then you can't do without additional work. In some schools, teachers take written assignments seriously - they check them against all parameters, give feedback. But I've seen this several times in my life, usually the attitude is formal. A school teacher must necessarily be an examiner of the Unified State Exam, understand by what criteria each assignment is assessed, for which points are reduced. For example, an essay in the Unified State Exam in English is assessed on five parameters, two of the oral parts - on three parameters. The assessment system is quite complex, an experienced teacher should be.
You can take a course that will give you the opportunity to increase your vocabulary (and in the USE in foreign languages this is the most important thing), improve grammar, improve listening skills, understand the strategy for performing various tasks, and then take a certain amount classes with a private teacher, with whom to work through the written and oral part, as well as identify gaps in knowledge. From experience I can say that the student often makes mistakes in a number of grammatical constructions and does not always understand how to compare statements in listening. But still, the main mistakes are made in the oral and written parts, especially in the essay, where, unlike oral assignments, it is impossible to complete the task following the scheme.
Ask course administrators to watch at least one free lesson before paying for the full course. You will immediately have an idea of how the lesson is going, whether the explanations are clear to you, how interactive these classes are, how many tasks the students themselves complete. The lecture format is definitely not suitable for preparing for the exam.
When choosing a tutor, see if he can clearly explain how he evaluates written and oral assignments. If yes, and at the same time, he can give a point for the completed tasks and clearly explain by what parameter the grade was lowered - this tutor is yours! You can study in pairs with private teachers, find a person with approximately the same level of knowledge and aspirations. Efficiency does not suffer from this, and the price for each will be less.
It's hard to say about the Olympiads. If this is preparation for the Olympiad in the university where the Olympiad will be held, then it makes sense. Each university has its own format, the Olympiads are held in two stages, each stage is a separate story. The format of assignments in universities is constantly changing, all of this must be taken into account in the courses. Again, lookRead the preparation lesson, find the Olympiad tasks on the website. Do you understand the teacher's explanations? Does the instructor provide strategic instructions for completing the assignments? In the Olympiads in the humanities there is always a creative task. If your experience in writing essays, articles, reports is not enough, it is better to take a few consultations from a private teacher, write four to five works, sort out mistakes, work out weaker skills - some have literacy, others have problems with creativity, others not completely understand the structure and the necessary turns, the fourth do not own the style. And thus to reach perfection.
Be creative and ask the organizers and teachers questions about their knowledge and qualifications in evaluating USE and Olympiad assignments.