G292-Z20 nvme pcie gen3, what about bifurcation

Hello,
I just got my G292-Z20 and I saw after that, the U2 and NVME m2 are gen 3. even worst the second m2 is x2 only.
I need your opinion on a solution I came up with.
There are 2 pcie x16 gen4 at the back (SFF) and after some investigation it look like I can do bifurcation on those pcie.
should I get something like this https://a.co/d/655B8V6 and get few (3 or 4) m.2 in raid.
This server will have proxmox (install on m2 gen3 x4) and I would put vms on the raid with gpus in passthrough for AI.
I don’t think I need U.2 enterprise drive (first not sure if that backplane can support gen4 but when connected to the motherboard it is U.2 gen3 and only have 2 drives) I will also do external backups.
It look like the backplane was also made for multiples configurations maybe with a second pcie card I could connect the other bay on gen4 instead but might also be too expensive to do.
Otherwise, any suggestion on m.2 drives? I was thinking crucial T500 since they are on sales this week.

Thanks

After some test, the documentation says gen3 on the m.2 x4 but in linux lspci report the nvme running at 16GT/s (gen4)… now my question is does the U.2 is gen4 too

I decided to get 4x kioxia cm6 1.60tb used on ebay, it wasn’t too expensive. the server only have 2 ports but the backplane have the connectors to allow you to install more (or only U.2) these are the parts that are required
Questions about nvme raid card - #19 by timbit1123