There's a ton of sources, but gamersnexus did the most in depth coverage that spans many months and many videos. Stuff like https://www.youtube.com/watch?v=OVdmK1UGzGs&t=1s. Majority of all Intel 13000 and 14000 CPUs are effected. And the new generation that just came out just seems to have extremely poor performance for the money as compared to equivalent AMD CPUs that both perform better and cost less.
As for the power consumption, in the generation you are looking at they are about the same or Intel is worse. In your build you picked i7-14700. Here's a decent read from gamersnexus again: https://gamersnexus.net/cpus/intel-desperate-i7-14700k-cpu-review-benchmarks-gaming-power. Give it a read and then go with an AMD processor :)
I have a Synology. I love it, but if you’re on a budget build one server and use that for storage and hosting all your stuff.
Use PCPartsPicker and build yourself a full desktop tower. Something like https://pcpartpicker.com/list/gHLHxg. You can get a lot for your money on the used market, but it will use way more power and will be slower.
For above build I picked lower to mid range components, but you can see what matters to you most. Maybe get a CPU with more cores and less storage to start and add more storage later. Or do the opposite if you don’t care about CPU but want more storage now.
Some hardware notes, do get AMD CPU and stay away from Intel. Last 2 years of their CPUs are plagued with major issues. Do also get DDR5 ram and whatever motherboard supports that. Get a fast NVMe for your OS drive. 1Tb should be plenty.
Finally don’t install Ubuntu on it. Two options for OS: if you want to use it as a nas then use TrueNAS Scale otherwise use ProxMox. Then you can create a virtual machine on either one of those and install Ubuntu on that if you still want to. You can also run containers on both of those.
You need to understand what Proxmox gives you, which primarily is ability to run/manage/backup/etc VMs easily. If you don’t care about that, don’t use it. I have a fairly well spec’d desktop I use for homelab and I use proxmox because I often do experiments in VMs where snapshots and ability to jump to snapshots is essential. So is being able to spin up a new VM with new OS (like Windows) for example to do some testing. You can still do VMs without proxmox, but proxmox does make it a lot easier for living with daily.