whatever bike mounted bag you get make sure you pack it well. The contents get rattled about a LOT more than they do in bags attached to you. Had a particularly long period without punctures on the commuter, when I eventually opened my bag to find a tube “sawn” open by the threaded valve, spare disc pads polished/worn and the contents of the puncture repair kit a mess. Everything gets wrapped in a bit of rag now.
Saddle packs are good, had a topeak wedge for a while, was nice but eventually the stitching on the straps went, and they can obstruct seatpost mounted lights. Currently using an aldi clip on number, it’s lasting so far. I used a Deuter frame bag over winter (and on other bikes for short rides when I don’t want a pack) works well, but gets in the way when grabbing bike to haul it over obstacles and if you want to use bottles. (and may not work on some suspension/weird frames)