No, they're not too loud at all, well not to me anyway. It's obviously all a matter of personal taste and depends on what other 'models' you have in your head for this genre of music, but i must confess if I were mixing this track I would make the drums even louder! This is because to me the piece doesn't sound like an ethereal 'whispy' piece about time travel; it more reminds me of a band like King Crimson and as such it would have rock band hallmarks such as the style of guitar sounds you've recorded, and reasonably aggressive drums to match. Well, that's just the way I hear it!

On mixing - this is an enormous area and learning how to get the mixes we're hearing in our heads is a lifelong learning experience I believe. I once contacted some guys on the Sonar forum who posted a song that had the kind of mix I like, crisp and clear and powerful where it needed to be. I kept their reply in the binder that I keep of all my notes that I gather on techniques, and it's in this Word document. Check it out and see if it helps:
Mixing Tips

Regards
John

Songs web site
YouTube Channel
BIAB 2019
Cakewalk by BandLab
Studio One 4