My hardtails have plenty of space to run a Alpkit medium fuel pod in the triangle- fixed to the TT and ST. This fits everything I need- multitool, tubless kit, tube, levers, mini pump, spare battery, phone and cash. Bag swaps between bikes in seconds.
My FS has no space to run the bag out the way so I fix a multitool to the back of the bottle cage, attach the mini pump to the side of the bottle cage, run a spare tube in the TT/DT gap and strap some levers to the CS. Phone and cash lives in pockets.
I run tubeless but always carry a tube for those ‘worst case’ rides. Both solutions are neat and I’ve not found that I need to carry more than this. I sometimes carry a bag for longer rides- food, layers, waterproof and more water.