I have an APC metered PDU (AP8870) that gives me power, temp, and humidity stats for the rack

Have you gotten into the RBSU and changed the power profile to “Minimum Power Usage”?

Really kinda depends on your use case.

For instance, if I’m building an ESXi cluster, then yea HPE all the way. It’s quite trivial to find the option parts I need to complete the build and scour eBay for them. With those components tested and certified to work together I shouldn’t have to worry too much about weird issues popping up.

Now, on the other hand, when building a NAS / SAN, I don’t want to be locked into buying HPE branded disks so I opt for a Supermicro system. It doesn’t care what brand of disk you use so I’m free to buy what makes sense for the type of datastore I’m creating,

Supermicro is also one of the few who build their server platforms on standard ATX / EATX form factors, so it’s pretty easy to get the chassis you like and build the insides out however you like. Also makes upgrading the server internals super easy. Just buy a later gen components and transplant them. They’re very good about making documentation and compatibility matrices available online

The way to do this with an L3 managed switch is to use inter-vlan routing and access control lists.

First part is simple enough, enable IP routing in the switch, then give your vlan interfaces an IP address.

To control which nets can talk to others you build ACLs and attach the policy to the vlan. For instance, you can permit your workstation on the main net to talk to anything on nets 2, 3, and 4, and conversely they can talk back to only your workstation if you wish. Then you can deny anything on nets 2 - 4 from talking to each other.