1- Mini pc's from start9 & umbrel are at minimum 8gb/16gb so am wondering if my 4gb mini is sufficient for at least Core but i have 1TB memory.
I think I only had 4GB on a RPi when I first started playing with Umbrel. It worked, and that was when it ran on top of another OS. I would imagine now that it's integrated with it's own trimmed down version of Debian, it should still work. I don't think it'll bog down too much, and it doesn't hurt to try if you already have the PC. Just keep in mind that if your hard drive is a spinner that's going to be the bottle neck regardless of how much ram you have.
If you're buying a new PC for the purpose, get one with at least 16GB and a 2TB nvme SSD. You wont regret the extra expense.
I have
one of these mini Dell PCs currently running Umbrel. Mine has 32GB if ram, a 256GB SSD for the OS, and I mapped a 2TB nvme to /home, which is where Umbrel wants to store it's files.
FYI if you find yourself with one of these mini Dell PCs, I don't recommend attempting to duplicate my HD setup for the faint of heart. Every time Umbrell updates it's self, it overwrites my fstab file. Unless you're skilled with Linux, you're better off just using either a SATA SSD or the nvme, and not attempt to use both.
I've salvaged many of those mini Dells from local school/library auctions and bult nodes for friends and family on quite a few of them. I believe the one in the link does have an nvme slot, most of the models I've seen with i5 processors do.
2- Start9's more expensive model has " Intel® Management Engine (IME) disabled ". How critical is this ? Should i care ?
It is in fact critical to have it disabled. It's got all kinds of security issues with it, and isn't necessary at all.