Just at this U18 level (and younger) there is no such thing as "the same level", eliteprospects are using "Russia U18" as the umbrella term for it, but in reality it is a combination of U18 regional leagues that really vary by strength. The strongest one unsurprisingly is the Moscow region league, followed by St.Petersburg, then probably Volga and Ural regions and the weaker ones would be the Far East/Siberia and Southern regions (I'm maybe mistaken somewhere there, but that's the general idea). And it is a bit of a vicious circle there, as strong players want to play in the stronger league, moving there and making their home region's league weaker and their new league even stronger.
Inside those regional leagues these is also a historical division in weaker and stronger hockey schools/programs, Traktor is a historically strong school and Admiral is a relatively new and a weaker one. So to compare, Vitaly played for a strong Traktor team in a relatively strong Ural U18 league, while Matvei plays on a weaker Admiral team in a Siberia/Far East league that is also considered a weaker one. So even though in eliteprospects it might look similar, the reality quite differs.