What Fred said
Strapless riding defo easier on the body, but you need to learn the proper technique too, so a brief time for the learning curve and you'll be grand.
I am 70kg and have a 5/8 Aviso Lost Round Nose Fish...and LOVE it. I have had this board for over 6 years and ridden the piss out of it all over the world, easily 500 sessions, lots of scratches (I have a painted version) but no dings! This board was made for surfing but it has been super durable. Would buy another in a heartbeat. This shape has a fair amount of volume so you don't need too long of a board. The deck is fairly wide so the board is super stable and footwork is super easy.
As Fred mentioned the deck of the Aviso boards "give" and they are super cush on the feet and legs...and the board rips in anything up to head + 1/2 surf...and also a sweet ride on flat water.
you can ride the Zone strapless, but this is basically my strapped board....for when it's nuking and really gnarly. My Zone is pretty small and switching stance on the fly is very tricky so I ride this board mostly goofy stance...and sometimes I will switch stance if I am trying to make bigger upwind gains on my port tacks.
One thing about riding strapless is that you won't be using the same muscles as with a TT, especially stomach muscles which get a huge workout when doing jumps and aerial tricks...so don't let yourself lose that 6-pack...haha
The other thing that I feel is important is using kites that have easy bar pressure/steering because you will be riding one handed a lot with a surfboard...
lastly, if you are going the route of a surfboard that has strap option...just start strapless...you will learn a lot faster and better technique and proper stance WITHOUT straps...just make sure your board has good deck traction, either good wax or a good pad.
I hope the strapless surfboard helps solve your problem!