Had a quite long reply to this, and MG ate it with their goofy "login" thing. Eh...screw it...
Simply put: get a bigger case for not much more $$$, like a Doepfer LC9 or Tiptop Mantis. Don't build things like this, as "full systems" in these tiny cases tend to never work as expected. And take more than a week to research this; many MG users will pore over their builds for literally MONTHS, because that's the degree of attention and research involved in REALLY nailing a build that, when all of the stuff shows up, works as you'd want from Square One.
Consider a Behringer 2600, also. It's perhaps the best educational system for learning both analog synthesis AND initial modular explorations. It also only costs $650 over here; right now, Thomann UK has them on holiday sale for UKP 469. Add some basic sequencing, such as a Korg SQ-1, and you'll have something that just five years ago would've set you back about $10k (ARP 2600 + 1604 sequencer). Yes, people do bitch about Uli and his antics, myself included...but this isn't some Shenzhen backalley knockoff. It works and sounds like a new or recently out of the box ARP 2600, and yes, I did get to use one of the v.4 "orange" ones new way back in 1980, pretty much right out of the box. It plays very nicely with Eurorack or any other system that uses 1V/8va scaling and positive trig/gates. Plus, this thing's built like a tank, and it's rackmountable in an 8U roadcase...as opposed to Korg's 2600M, which is missing the 3620 keyboards "extras" (which are on the B.2600, which is smaller...?), looks rather cheap for something that runs around $2k, and doesn't share in the portability of either the 2600FS (had the wood/tolex case, like the original) or an original ARP.
Another learning tool: VCV Rack. It's called a "Eurorack simulator" for very good reasons. It's also free, and you can get hundreds of modules for the system for free as well...with some others being VERY cheap. And there's emulations of modules you'll find on here, often designed and programmed with the cooperation of those Eurorack manufacturers.
Lastly, don't believe everything you see and hear on YouTube. While some of us CAN do tiny builds like this, more often than not these are "mission-specific" things, such as a rework I did for sacguy71 to add a few things to a sequencing/control Palette 104. This is actually intended as a companion to an endorphin.es Shuttle System and, undoubtedly, a few other toys as well. When you see someone on YT shilling for a do-it-all minibuild that presumably contains a full-on modular with everything needed, and their studio looks like a Hollywood set (ergo, pretty much unused), DO NOT TRUST THEM. Real working studios tend to be more messy...cables all over, big stacks of gear, lots of notes stuck here and there, and the like. And YT still has an under-the-table problem with presenters getting "considerations" from firms whose equipment they're using. This is something that's gone on for years...I experienced a "push" toward that a few times when writing for "Recording", a gig I'd had enough of when it became clear that it required me to compromise some of my ethics.