Late 2015 4gb base - os reccomends?

I am loving oclp and have used it on a mini 2012 model with Ventura for my mum and my own 2008 MacBook now runs Monterey. I have left my 2009 MacBook Pro on snow leopard because it’s only job is FireWire tape transfer and it aces it. I have an old base 2015 iMac which is a lovely screen but I can’t use it as a 2nd monitor for my M4 macmini as it doesn’t support target display mode. I was wondering if it’s worth oclp’ing it and sticking on a newer OS but only being 4GB ram I am not sure what it will handle ok? It was a gift so can’t complain as d have fed it 16gb at purchase otherwise. Use will be browsing maybe minor 1080p editing but the M4 beasts 4k easy so the iMac will be taking it easy now. Wish Apple had left it easy to upgrade the ram but it’s soldered on this model. BTW isn’t OCLP amazing ! Respect to the devs.