BIAB is great for traditional jazz and country. Not so much for pop or contemporary jazz (you had mentioned you were interested in backing tracks for pop as well). For those genres my go-to is smoothjazzbackingtracks.com and karaoke-version.com. If you have the budget, there are also services that can create customized backing tracks for you (e.g., if I see a performance I really like on Youtube and I want the same arrangement, there is a guy who lives in France that I pay to create the backing track for me... he's really good). Another underrated source is Youtube itself. There is a plethora of really good backing tracks there that you can download and use (you'll need one of those Youtube to MP3 converter software).
I've had the BIAB Ultrapak+ for about 4 years now and currently have the 2020 version complete with all the RealTracks and all the styles... it has gotten better in genres other than traditional jazz and country over the years I've had it, but it's still limited and you will have to spend a considerable amount of time looking for the appropriate style to fit the track you're creating (unless it's traditional jazz or country), and even then it won't be that great.