I agree that the raw tape is ugly: the LEDs themselves are painfully bright, they change colour and brightness seen from an angle, and the tape is never 100% straight or flat. Only ever use it where it won’t be seen. The profiles are nice, act as a heat sink, and you can get diffuser covers, but can cost more than the tape.
You can successfully stick the plain tape even upside-down, but you need to clean the surface carefully, take great care sticking it down to avoid bumps and wrinkles, and make sure that the ends can’t peel off. Use a clip or glue particularly on the power supply end. The waterproof strips are heavier and might need some additional glue. High power strips can get hot and soften the glue. Works best on very smooth surfaces, no chance on anything textured without extra help like some hot-glue.