would you reccommend the b450 or the b550 mbo for it? i think ill just re use my ssd, HD, psu and gpu for the time being until gpu prices go down unles you think there will be any problems with that?
A B450 would be fine if you find one at a bargain price, but otherwise you might as well go B550 - there used to be a £40-£50 premium for the B550, but that is gone now as you'll find the entry level B550's for £80-£100.
Don't worry about going for the top of the range boards - even the Asustek or the very entry level boards from the big manufacturers should be fine: personally I have a preference for Asus, but I won't bad-mouth anything else that I haven't researched. Likewise I have a preference of avoiding the WiFi/fancy extras unless there's something that I can't add of my own accord (you can keep the WiFi more up to date if it's just your own choice of PCI-E card). The only reason for going for anything more than the entry level is if you REALLY need 3 or 4 onboard NVME slots - clearly NOT your use-case!
Pro's and Con's:
The only "con" of the B550 is around price: a small price premium if you['re buying new. The main price difference now is due to being less likely to find a heavily discounted or second hand one.
The obvious pro's are the PCI-E gen4 for future upgrades (GPU + NVME) and some of the B550 boards have multiple NVME slots, which is a nice-to-have. The less obvious and my main reason is that the B550 spec for the VRM's is a nice little step up (I forget the exact changes, but that was the reason given for some of the initial price increases), which would allow you to upgrade to a 5900X or 5950X in a few years' time. Technically a B450 could handle those, but I gather that the older motherboard spec has the VRM's are a little stretched with the top-end CPU's. Not worth paying a huge premium for, but I like the idea of better VRM stability for the short term to have the BIG step up as an option later.
Honestly - the rest of the kit will probably be fine. If you're feeling flush and holding off for further GPU price-drops, I would recommend a small NVME as a boot drive - even something like a WD Blue SN550 (500Gb?) would absolutely wipe the floor with even the very best SSD... and you could still keep the SSD for games. I used to have pretty decent SSD's (2x Samsung 850 PRO's in RAID0) and I was blown away with how much faster the NVME's are.