I haven't used Inkscape for a while and currently have v. 0.92.4 installed. I used to use this a lot and was familiar with the tools, interface etc. Would I be able to install the current v1.3 at the same time to "practice" on getting used to the new interface whilst at the same time keeping the older version in case I'm slow to learn the newer version?

I hesitate to say yes, because the new version can be setup to look and work like the old (pre 1.0) versions. They both will point at the same preferences location, unless you have a dual-boot computer.

There is so much to love about the 1.3...  We still have .92x at the shop, but we will migrate to 1.3 this month. I have been holding off the migration (12 computers) until the 1.x.x version was user-friendly to all the .92.x users.

The changes that may catch you are the order of tools on the left has changed (but it can be modified) and the snap toolbar is a popover unless you set it to constant in the preferences>Interface>toolbars.