If you are going to have optical prints made on RA4 paper Ektar is the most suitable film for what you want. Portra and 400H are less saturated and the consumer films not available AFAIK in 120.
Yes you can also do as suggested and shoot Velvia and have it scanned then output to RA4, but slide/chrome/whatever film has a very narrow range. Exposure is much more critical and even slightly high contrast scenes present a choice of losing highlight detail or shadow detail, or maybe some of both. Velvia is worse in this regard than Provia. Unless I were able to control the lighting or going into very well known, fairly low contrast lighting (overcast days for example) I would still favor the Ektar when the intended output is prints. But I admit I've never really gotten along with Velvia. I do shoot slides for projection, but mainly Provia and my dwindling frozen stock of E100G.
It doesn't do you any good now but the old Agfa Ultra 50 was the closest thing to a negative film with Velvia- like saturation I've ever seen. There are only a minority of times I really like over the top saturation but when I did want that, boy did it deliver. I still miss it.