I went for Duramat to cover my 4x6M garage floor over 2-years ago. I park a car on it and often work in there. It's stood up to car jacks, axle stands, oil, brake and other fluids being spilt and also sitting submerged in crappy water after a crazy heavy downpour that ended up leaking into the garage. My garage has a 300mm thick concrete base and 3x of the walls are retaining walls for the surrounding earth so it can feel a bit cold in there, but the flooring definitely helped make it feel a bit more insulated. It's certainly much nicer to work in there than before the tiles. Considered just painting or sealing the floor but it would have still been mega cold.
For my internal edges, I cut the external interlockers off one side and left the internal interlockers where they were and used it as a straight edge, I have battens and insulation on the walls so you can't see the internal interlockers. I had to cut more than just the external interlockers off some pieces and tried cutting them with a new sharp Stanley blade but it took too much effort so ended up sawing them in the end. Rubber mallet to get them down easy enough and they've been been fine. It is worth leaving a 1-2cm gap around the edge as they can move ever so slightly if in direct sunlight of if it's very hot.