Hi
I had to google Acrylux as I'd never heard of it, so it seems its L&P, however Gellux is Gel Polish. NSI L&P and NSI Gel are both predominently for extensions/overlays.
You need to decide what route you want to go down, you cannot create exensions with Gel Polish, so is it extensions/overlays you want to do, or just Gel Polish - as you've been out for a while things have moved on a bit, and lots of new techs are able to run successful businesses solely on natural nail manicures and Gel Polish, however....lots of them are starting to ask about extension training.
NSI L&P & Gel are both good products with good reputations, but Capital training can be a bit hit and miss. Some Capital Stores have in-store employed trainers, some are just locations for travelling reps/trainers. If you use the search option on here you will see varying opinions on the training levels offered by them.
Depending on how rusty you feel, you may find a one-day course is not enough to refresh your skills, especially if they are trying to cover 2 different systems in one. CND for instance do a 2 day course just to train in Shellec (their Gel Polish equivalent) so 1 day for two completely different systems is likely to leave you with knowledge gaps, meaning you'll need more training = most cost.