You can charge the 100AH battery at the spec max of 25 amps, but you can also charge it at a lower rate no problem, just not at a higher rate. The key is to do it at the right voltage.
That is the same for other types of battery. My 100AH AGM said max amps was 27 amps at the spec charging voltage. You can charge at 15 amps if you want- it just takes longer, as long as you do the voltage.
Solar is no problem unless you have a big array and a small bank, but that is no different from many AGMs (Lifelines excepted we are told)
I can also use my 55 amp converter on them when they will only accept 35 amps, same as any battery that is up there in SOC when you start the recharge. The charger only does what the battery will accept and tapers from there.
The problem only arises when at a lower SOC the battery will accept 75 amps but the spec says 55 is max. So don't use the 75 amper, use the 55 amper.