"I'm keen to understand your preferred strategies for this scenario. If possible, could you provide examples or share your experiences?" Well then, probably wouldn't hurt to see how Mr Bolton generated his modular weapon: https://polycount.com/discussion/166058/ak-337-modular-rifle-system
Welcome! I recommend familiarizing yourself with the forums' search function to find similar threads, for example at-what-point-do-i-use-more-than-one-texture-set-for-a-weapon, texel-density-and-number-of-uv-sets-on-a-model, best-practice-for-modular-weapon-uv-textures, ...) And the wiki can be useful to read up on general…