Been through this exact headache with a few sign builds, so here's what actually works. Voltage drop on 12V strip is just physics, the copper traces on the strip itself are thin, so by the time you're a few metres in there's not much voltage left and the last section looks washed out and yellowish compared to the start. It happens with cheap strip and good strip alike, better quality just delays it a bit.
The fix that made the biggest difference for me was feeding power at both ends of the run instead of one. Solder a second pair of wires to the 12V and ground pads at the far end and hook them back to the same supply. That alone cut the visible difference dramatically, beacuse each end is now only pushing half the distance. On longer runs you can add a feed in the middle too, so no single stretch of strip carries the whole load. For keeping things tidy, I run the injection wire behind the backing board or inside the channel the sign sits in, so it's invisible once mounted. Use wire that's a decent thickness, something like the mains flex you'd use for a lamp rather than thin bell wire, otherwise you just move the drop into your wiring instead. Don't rely on the adhesive backing for the second feed, put a small dab of glue or a clip over the solder joints so they don't lift off over time.