I would strongly recommend astia 100F, especially if you are new to slide film and uncertain about the lighting conditions (particularly the contrast). This is a film with neutral tone and a good ability to hold highlights. It also scans very well. Astia can also deliver pleasing skin tones.
In my experience, provia has poor neutrality if color temp isn't just right, and none of the velvias have the latitude of astia. I do like velvia 100 for some subjects but if you have light peeking through clouds or reflecting off water velvia is not the right choice in my opinion. And neither is provia, because you probably won't be at 5000K in overcast conditions.
Among the fuji slide films, my other favourite is provia 400x, which I like far more than provia 100F. But alas it is not available in 4x5.
Put a 612 back on your 4x5 and bracket!!! Just a thought.
P.S. And I salute your decision to shoot slide, it has a unique power and, particularly in overcast conditions, can really sing. Analoguers should be shooting slide like crazy right now- we don't know how much longer we will have it and it provides for some amazing analogue slideshow presentations... and amazing scans and prints too.