Sounds good, if the 190w solar (supporting 12v batteries) can remain present while the big array is added. Assuming this to be a traveling RV, there are also engine-based DC->DC options for supporting the "house" 12v battery bank, even if the batteries are of different types (SLA "engine" and "LFP" house being the typical issue to be addressed).
I don't think that any of the 'simple but dumb' buck converters can handle the 12v destination load (or bus) being charged by any other power source (including both the "12v solar" SCC, and any engine-related DC->DC charger or hard-wired interconnect.). They are built to be the sole source of power when used, and will lose the "magic blue smoke" when high "12v" voltage (provided by the battery or another charger) attempts to override their own output-only voltage regulation circuits. (They can't be run backwards at all.) The Victron can definitely handle that situation, at higher cost.