First things first, bare in mind I'm the most active idiot on the forums. :) Second things second I use and adore TADST so here's a link to a post I compiled for how to get yourself setup. https://forums.bistudio.com/topic/159708-alive-advanced-light-infantry-virtual-environment/page-342#entry2937748
SP is not recommended if you want to use the full ALiVE suite. TADST is a dedicated server tool which will allow you to enable persistence in your mission(s) and save your progress to ALiVE's War Room. This ensures good performance and the ability to "save" and "load" while using multiplayer. For me, persistence is key. I hate the idea of my mission progress not saving so this alone is brilliant for my needs. When I'm done for the night I "server save and exit" and the next day I can continue my mission again. It's awesome.
When I first got into ALiVE, Autigergrad (mission maker. All around good dude. He has some missions here and on BIS and Workshop) turned me on to Assymetrical insurgency missions. You can learn more about Assymetrical missions here: http://alivemod.com/wiki/index.php/Insurgency
So this is really all I can speak to. It's my favorite mission type and really the only thing I play. It's also excellent for solo players and small groups because there's more to do than just kill dudes. What I try to do is replicate the war in Afghanistan circa 2009(ish). Good guys versus the Taliban. Also excellent for small groups because they really shouldn't be overpowering you unless they overwhelm you with numbers.
What I like to do when I make my missions (I have one in the mission template thread. Two more coming soon) is to group 5-6 "playable" units to me. These are generally my AI teammates, but I leave them on "playable" in the event I make some friends someday that want to play with me. :) But it also ensures I am never out there alone. I also use SpyderAddons in all my missions, not only because it adds so much life to ALiVE (ambience, conversation trees with civs, etc), but because it also allows me to have an AI spawner in the event I need more warm bodies to tackle an objective and also a vehicle spawner too: http://steamcommunity.com/sharedfiles/filedetails/?id=579263829
Sorry if the next bit of stuff is a little inside baseball. What I like to do when making my missions is to place a "safe zone" around my base. A decent size TAOR so when I get going initially I'm not immediately inundated with OPFOR. Generally I'll place the opposing Assymetric side's Military Commander module pretty far away from my base so the insurgency starts as far away from my base as possible. When the mission starts my "job" is to go around interrogating civilians in the nearby towns, trying to get a leg up on where OPFOR is doing its dirty work.
For my side's Military Commander I like to have more units than the OPFOR side to start. So I start out a little more powerful. OPFOR will recruit more units from the civilian population as things get going (Civilian Population and Civilian Placement Modules are required for this. I usually place several Civilian Placement modules so the missions are jam packed with civs. OPFOR can recruit a ton of you're not careful).
Once the basics of the mission is made, I then like to manually add some more enemies (syncing them to the virtual AI module) as far away from my base as possible too. This simulates a 'the further from base you go, the more dangerous the game gets' kind of thing. I then like to pair that with a high priority custom objective module on the other end of the map too. This increases the likelihood of OPFOR being numerous on the opposite end of the map.
After placing all the modules and having a basic functioning mission going, the first thing I do is debug the virtual AI module. I then enter the mission and look at the map. Areas populated by BLUFOR and OPFOR will start lighting up. I take note of the empty areas. I then exit out and do this a few more times. If certain areas of the map never get populated by OPFOR, I'll generally place some custom objectives over these dead areas. Or, if the dead areas are only in the hills/valleys, I'll place markers over those spots, add another military objective module for OPFOR, set "random camps to medium, whitelist the module to only populate enemies in those areas. This means any area on the map *can* be dangerous.
Because I'm usually playing alone, and also because I'm trying to replicate a very specific kind of real life terrorism mission, I don't generally like to let either side use a ton of air vehicles or tanks or what have you. I keep it mostly infantry and light vehicle based. I'm also not a particularly good player. Lately I've been messing around with more conventional all-out-warfare missions too so I hope in the future I'll be able to balance those to a more SP/small group oriented experience as well. But for now, setting that kind of thing up is a little out of my league.
I have a lot more I could say and many more proncipals I could share but I don't want to overwhelm or confuse you. If you have any specific questions let me know and I'll do my best to help.