How to play Xcomfiles:
Step 1. Realize that shooting anything in serious missions is stupid since everything in cults past the basic level has sniper/spotter. Everything. If you are seen in a mission you can expect at least 10 enemies autofiring at you and 2-3 grenades being thrown at you per turn. Thankfully your shield has about a 50/50 shot of shrugging off small arms fire but grenades will fuck your day up really quick.
Step 2. Capture a bat and train it. If you can't get a bat then get a rat. They have 100%/70% sight vision through smoke respectively along with bonus sight range, anti-camo for enemies like ninjas, and camo of their own.
Step 3. Every soldier gets a shield, a magnum (only used if you need to find the one asshole on the map who refuses to panic), rest dynamite/incendiary/grenades.
Step 4. Start mission. If something can see you, abort immediately. It's not worth it, just take the -100 score hit and try again.
Step 5. If you're not spotted, drop smoke and spam dynamite with every character every turn. Your bat/rat can see well enough to spot most enemies well before they can get to you.
Hopefully you can kill everything before any enemy unit sees any of your units. There's still a 50/50 chance that some asshole will spend all of his TUs randomly running straight at your group of troops in which case god help you I hope it doesn't happen on turn 2/3 or you're gonna get smited off the face of the earth by grenades.
Ideally your soldiers are all bio-enhanced and all that shit with 65+ strength who can throw dynamite pretty far, but sometimes you need grenades to really get range. Another trick is (because for some reason the mod forced explosive height to 2) to stack 4+ dynamite ontop of a structure and have it literally blow through multiple levels in a single turn.
Average fight:
You can see how even making the place look like its been carpet bombed doesn't stop them continually threatening to get close enough to see you:
Red dawn seem to be the worst when it comes to lobbing grenades across the map at you as soon as a single character is spotted. I guess its supposed to be some Russian artillery meme? Black Lotus by far the easiest, they seem to have the worst/least snipers and no grenades (they have stealth ninjas but your bats can see or echolocate them fairly well). Exalt being the 2nd worst to fight and Church of Dagon being only slightly harder than Black Lotus. When it comes to the final assaults you either play like this for the outdoors bases (Red Dawn/Dagon, although Red Dawn has a massive underground base but I just waited them out) or just spam proximity grenades if its an indoors one (Black Lotus/Exalt).
I barely got the research to unlock promotion 3 before 1999, which is when I'm "supposed" to get it to match the original timeline. Still behind on research when you count that I haven't unlocked things like Skyranger or better labs or large radar. But on the other hand I have a full 8 bases set up with a minimum of 20 defenders in each base all being trained up to excellent stat levels by gyms and pre-screened for over 50 psi strength, on top of 22M in the bank. I also have like 250 elerium and lots of alloys and plasma weapons in storage along with a floater navigator. My main 2 bases combined are full of over 70 roided up genemodded bioenhanced supersoldiers (only thing they don't all have is ninja training because it requires 65 melee accuracy while you can only gym up to 60, which means manual training which I've not really done much of). What's hilarious is that I did get a base assault by like 10 floaters in December 1998 (apparently "the invasion begins 1999" is a lie), but my literal scrub base tore them apart with their magnums. Welcome to earth motherfuckers, you're like the 10th most dangerous thing we're fighting right behind giant scorpion terror missions so please take a seat and wait your turn.