I understand using Serializationisbad or any exploit alternative is an important mod these days.
Gregtech is pretty self-inclusive now taking ideas from other mods and incorporating them into its own, so most mods will overlap a little in general. As Greg says he’s taken steps to make pretty much all mods work under Gregtech and nothing will really break or be incompatible with it, aside from I think Mekanism which had recipes that made things way to easy even with Gregtech installed and The Aether which Gregtech didn’t seem to like its blocks or logs, but I think Greg added compatibility with that recently. The Thermal series of mods and MinefactoryReloaded can add machines that could make progression too easy but many of their recipes require higher tier materials so that’s up to you.
All the tech mods work with or alongside Gregtech, Buildcraft, IC2, Immersive engineering, etc but nothing really adds anything that Gregtech doesn’t. Though Immersive engineering’s blast furnace might be an issue if you are looking to progress purely in Gregtech, it’s somewhat easier to build that than cobble together the technique to produce steel with the crucible.
Quality of life mods wouldn’t impact Gregtech, nor stability mods. I would recommend any of the following:
SoundFilters: alters sound to better reflect the reverb you would expect based on block material and space.
Mob-no-render: culls mobs you wouldn’t normally see, meant to improve performance.
Leafculling: same for leaves as above
No-mobs-on-trees: meant to stop weird mob spawns.
BetterFoliage: makes things appear less square, though i would recommend turning off the log feature and just keep the leaves.
Betterrain is a good mod to add too, but I can’t find a source for it that isn’t a 9minecraft website, so I won’t link that here. It makes rain more atmospheric and less like someone flicked a switch.
AquaTweaks: fills in spaces where you would expect to see water like around fenceposts etc, usually looks better but your mileage may vary.
loading-progress-bar: gives just that little bit extra detail while waiting for minecraft to load
Ding: makes a ‘ding’ sound when minecraft has loaded, trust me it helps.
HelpFixer: removes problematic and broken commands that might cause bugs, this is only really good if you have large modpacks and probably wouldn’t be that helpful here.
You should also note that there are a variety of mixin and bug fixing mods out there like unimixins, gastation, bugtorch, neodymium, falsetweaks, etc that all have their own incompatibilities with each other and may make any of the others obsolete so yeah, take from that what you will.
There is also Etfuturum Requiem, Twilight forest, Netherlicious and Hardcore ender expansion that expands or augments Minecraft in general, they all function alongside Gregtech perfectly fine. Pams Harvestcraft can also be added if you want to add more farming options.