Egpu help

There have been a few posts about egpus. I am looking for a little 101 in regards to resolve.

Questions.
Expectations of a internal 16gb iMac gpu and a Egpu of same caliber VS all internal gpu (pc)

Do I need to run a second monitor to “activate” the egpu?

Basically I am comparing a fully built iMac with max128 ram and card with egpu with 16gb ram VS a PC of similar build with a 3090. Can’t find the sweet spot on the Mac for a reasonable price. Not having pro-res export is my biggest hang up. Anyone have a work around (exporting master file in resolve then versioning in premiere?).

Having a very hard time pulling the PC trigger as I’ve been Mac based for 15 years.

1. Never buy RAM from Apple. AFAIK, you can still put third-party RAM into an iMac by yourself.
1a Do you really need that much RAM?
2. An eGPU will run without a monitor plugged in. It has no RAM, that is VRAM.
3. VRAM doesn't add up, so if you need more VRAM, go for the 3090 in a PC.
4. You can have ProRes export on the PC from Fusion.

There is no sweet spot on a Mac for a reasonable price, if you're comparing to PC, especially given the imminent release of Zen 3/RDNA2, and increased availability of Ampere cards. Lack of ProRes export is not a big deal, DNxHR/Cineform are perfectly adequate, or arguably better, as intermediate codecs, and you can export ProRes from Adobe products, or from something like Assimilate Scratch.