You can verify the current rating of the relay on the link you included. Isolators inherently create a voltage drop so some people dislike them although it is usually a simple matter to adjust the regulator to compensate. If you don't compensate for the voltage drop, the isolator will prevent effective re-charge, hence the popularity of combiners which are more operator-error-proof.
The ACR is a combiner. Stated another way, combiners are relays. Not sure who told you combiners are inferior but their advice and maybe their understanding is ambiguous.
Before you embark on any significant elec system upgrade, you would be better off to first clearly identify your ultimate needs by doing a simple energy audit of your boat as without that, you are designing a system which has no specific objective (to serve a specificed power need).