The 3700x is a 65w chip. It will be fine. Just enable PBO, and let it do its own thing. There is no such thing as future proof. Ryzen 6000 series will be a new socket, and most likely ddr5 ram.I don't think that a cheap mobo is ok for a ryzen 7, and I would buy a x570 for future-proof.
That's what I would do, stick with the b450. Just so you the know, the MPG X570 got horrible reviews because of really bad VRM performance, stay away from those. If later you do plan to upgrade your motherboard and want to stick with MSI the X570 Tomahawk is the way to go.Ok, so i will continue ti use my b450, thanks