Yes, it is good to work out what size fits and will it slip, what to do when sleeping, etc.
I was unexpectedly fortunate enough to get a pup whilst already had 2 Tollers (they are hard to come by). So bought a canvas collapsible crate for the back seat of my estate car and secured it with the seat belts. (Whilst other two were in dual cage in back). Pup managed to chew the mesh and escape whilst driving - not a good idea. I prefer the solid / collapsible crates. She'd probably be ok in one now but it's worth knowing the risk (and cost).
I have harnesses and attachment for the seats if I choose to do that - but don't want that to be my only option if weather is bad and I have filthy dogs. Hence I wanted crates. I already had one so bought an extra one and have measured that they will fit side by side in the habitation area with the bench pushed right back. However, I am currently also training the dogs to sleep together in one crate for travelling and also so that if I need to I can store more stuff behind driver / passenger seat (e.g. the dog fencing for shows as it is 1.5 m tall when rolled up), or if I end up needing / wanting to stop somewhere and have access to kitchen and a bench seat for myself.
I've also bought some "Gardman" mats that fit under the crate and stop it sliding around and smaller ones that fit inside the crate and I can put their vet bed on top of it without the bedding slipping. The Gardman mats are washable. Yee haa.
It all takes some thought and needs to be tailored for what you want. For most people with a Cali the flexibility to stop overnight anywhere and move on seems to be what they go for. For me that is less of an issue. On my own I didn't want a big vehicle to be driving or caravan to tow, so have gone for the Cali but then with awning and dog fencing. Not quick to set up or put away but should make our Cali life work for us.
As with many of these posts - have a think what will work for you and bare in mind the experience of others and you should do well
PS I only sent a PM to avoid a long to and fro messaging that may not be of interest to others.