Reloaders do stack multiplicatively, meaning each is equally good rather than getting better and better. The lowest your fire rate can get get 3 Reloaders and a fully leveled crewman is basically halved at 49.7%.

Is Automated reloader worth it FTL?

In the latter case an automated reloader is really good; the faster you kill the enemy, the less damage they'll do back. In the former case, it's not nearly as necessary.

Do augmentations stack in Ftl?

Most of the stat-boosting Augmentations stack with each other. The ones that don't stack are grayed out in stores if you already own one (or if all your augmentation slots are filled).