Hi there ...
I've gone the other way ... as you I'm a huge F1 fan and that's why I've been super excited when F1 mobile racing came out (since F1 mobile 2016 was amazing at the time) ... after many hours of racing F1 mobile racing and being active in the forum making suggestions (and being ignored by Codemaster unfortunately) I moved to RR3.
I get the point with the limited challenges (although the variety per track is much higher) but flow of the game is superior by miles and so is the graphic and the physics as well.
I've got 5 F1 cars so far (all earned by completing the GPs) some fully upgraded and I'm completing these challenges as well. Each car has it's own characteristics and is not just a skin.
I'm now waiting for the 2020 season and more tracks too.
Coming back to F1 mobile racing after the last update just reconfirmed my decision to leave I'm afraid ... Nothing has changed !!! ... and the game feels clunky and the graphics have fallen behind ...
So sad to see ... (again I've said that many times) ... unless there is a fully new game from Codemasters I will stick to RR3.
SORRY Codemaster ... it's in your hands.