Definitely free yourself from the rucksack if you can!
I got one of These in a sale a while back for a fiver I think, use it the Road bike takes two tubes/Co2 inflator + two carts/split links/multitool/tyre levers normally and if expanded can take near enough double the volume of stuff, crammed a spare emergency folding tyre in there for a bit of a mission me and a mate did last year…
For commuting I now use a £10 beam rack from ebay and one of These as it works a treat and I can roll up clothes kit and food and still have lot’s more space should I need it…
I’ve Managed a couple of bagless MTB rides lately too, the pair of Scott Roarban shorts I got last year have so many pockets I can comfortably get basic tools, phone and a CO2 inflator in the pockets, tape a tube to the frame, pop a bottle in the cage and I’m fine for 2-3 hours playing in the woods…