I assume 20 amps minimum per battery for fast charging and I think you said you would have 4x GC2. Could go 30 amps per battery but the benefit is marginal.
Yes IOTA-DLS with IQ along with Progressive Dynamics with Wizard are both good options. DLS-55 is fine just takes longer than 3 hours. 75 might overload one generator or run at max. Might have to run both and probably both with a DLS-90. If the 55 seems slow you can parallel a second and get a parallel IQ controller for 110 amps when running both generators.
PD tends to run a bit under rating so always choose 10+ amps more than you think you need. the 70 might be a good fit with a single generator.
I do not recommend WFCO except maybe the 100 amp model with a Boost button.
Can't recommend Boondocker either as it cuts out of boost at about 70% charged.
