Ariquitaun

It won't be enough. The second you start watching a couple of netflix streams at 4k your connection is going to be nearly at capacity and unless you have some sort of effective qos on the router you're going to suffer potentially from bufferbloat - increased latency which will make gaming agony

With a VPN. MAC filtering is trivial to work around.

I would never buy "a second laptop", that'd be unnecessary and wasteful. I have the one laptop I use for everything and take everywhere, plus the previous laptop as a backup. Right now this is an XPS 15 9560. Even though is in perfect nick the CPU (i7-7700HQ) just isn't strong enough to do the work I'm doing these days, therefore I've preordered a F16 and once I have it my XPS will be "the old laptop", my backup. The "old old" laptop gets donated to whoever needs one.

You contradict yourself on paragraphs 5 and 7. First you say it's reachable from the outside then it isn't.

DIY always better for an all around server which is a nas but also a application server.

I have an old i7-7700T with 32gb ram in a fractal node 304 case, running Ubuntu and 3x4tb drives in zfs raidz1. There's little it can't handle.