First of all, Thanks for the replies.
Actually i purchased 7DTD a long long time ago when it first came out and was super cheap, Not sure why i didn't get around to actually playing it but its definitely in my steam library so i will have to install that and have a bash!
See, I love Open world online survival games that you can choose you're path, I'm more of a "loot and base building" chill kind of guy these days rather than going hardcore PVP (Ie. Rust) But as many know in these type of games (especially online) you have to sink a TON of hours in and be online a lot to keep away pesky raiders and maintain base.
With that last line of your post, my advice when you try 7DTD is to turn off "blood moon" for your game. It's in the options. There are many options because 7DTD is intended to be a very user-changeable game. Some of the options are for creating a gameworld and can only be changed when doing so, but the "blood moon" options are one of the ones that can be changed at any time, before or during a playthrough. As well as that, a large proportion of the game is controlled by plain text XML files so with a bit of research you can mod the game a lot with nothing more than a text editor. Then there's the thousands of mods. And I mean "thousands" literally. Nexus alone lists >5000 mods for 7DTD and there's a whole site solely for 7DTD mods (
https://7daystodiemods.com/). The vanilla install of the game creates a subdirectory called "mods". Put a mod in there, job done. Load order is handled automatically and it works. The devs deliberately designed the game to be highly moddable because they understand that's the key to longevity. The only issue is version compatibility. Since 7DTD is still in alpha and still subject to major changes, new alphas often require new versions of a mod. No getting around that issue. Mods for older alphas might or might not still work.
"Blood moon" is the tower defence game-in-a-game in 7DTD. It creates a horde of zombies that are magically aware of your position at all times and which will come at you using the path of least resistance. The attack will last all night. The maximum number of zombies setting is only for the maximum number simultaneously. The more you kill, the more will spawn, maintaining the maximum number you set. It's intended to be incessant through the night. So you have to sink a lot of time into gathering materials, building a defence base, fighting the horde and repairing the damaged base afterwards to be ready for the next horde. Not my thing. Doesn't sound like it would be your thing. But it can easily be turned off in the settings. Or turned back on if, for example, you're well along in a playthrough and decide you want a horde attack for a change. Most players who like blood moon build two seperate bases. A home base for storing materials and crafting and a horde base for fighting the blood moon hordes.
7DTD doesn't have the "always active gameworld" issue. If you play single player, nothing will happen in the gameworld unless you're playing. It's technically an online game, but in the form of a virtual server for you only that only exists while you're playing. I don't know about how co-op PvE works in that respect. I only ever play solo.
In normal play, there is a chance of your base being attacked but only when you're in it or very close to it. There are two mechanics for that. The first is wandering zombies. Most zombies in the game are spawned in POIs and will only leave the POI if you're close enough for them to detect you and leave the POI to attack you. Some zombies are wandering and can appear anywhere. They're actually spawned in, of course, but the spawn point is "near where the player is now". In vanilla, this will be anything from a single zombie to a small group of zombies. Unless you mod the game for bigger wandering hordes (which I do, but which I wouldn't recommend for a new player). The second mechanic is one for which the balance is controversial - spawned summoners. They're known as "screamers" in 7DTD. They're zombies that summon zombies. The ingame mechanic/reasoning is that they scream very loudly, which attracts all nearby zombies. Hence the name. The screamers themselves are "attracted" (actually spawned) by activity (confusingly labelled as "heat" in the game). That can be all sorts of things. Lights. Noise. Smoke. Even just bright cloth. In effect, it mainly about running player-made workstations (most controversial being a dew collector for gathering water, which is completely silent), lighting (but not all lighting - the easiest workaround is to craft lamps for lighting as they create no "heat") and noise. Crucially, this only happens if you're close enough to your base. The gameworld is divided into fairly small chunks and only the chunk the player is in is active.
Finally, a few words on performance because 7DTD is atypical in that regard. Since it's a fully voxel world with constant realtime structural integrity calculations, the main load is on the CPU rather than the GPU.