Nice work. I like the subtlety of the mountains, the muted colors, the shapes. Nothing wrong with the mountain placement. A few of your rivers arise implausibly close to one shore then traverse a whole continent to empty in the opposite sea. Could happen, just think about how high the land would have to be right at that near shore, to force rain to run off a thousand miles the other way. Those two midcontinent big lakes would seem happier if they had outlets to the sea. Doesn't mean you have to give up encircling mountains - you could have what's called a water gap - in theory, cut by a young river AS the mountains arose. CAN have central seas, they just get mighty salty....

Your wave lines are nicely done, only they contrast a bit with the semi-photographic mountains. If the shores are hand-drawn (-looking) think how ye olde cartographer produced the subtly shaded lump-bumpy mountains.... could be made to work if they were a little more painterly or sketchy?

Caveat - if it pleases YOU, then press on.