https://www.homedepot.com/b/Bath-Showers-Shower-Stalls-Kits/Built-In-Shower-Seat/N-5yc1vZbza7Z1z1dvy9 More on reddit.com

That method kind of scares me; you have no backup plan in case you develop a water leak. On my shower in my forever home I created a waterproof box out of cement board and Redgard (a roll-on membrane). Then the shower kit was glued to those walls. I've planned for the worst, while hoping for the best. More on reddit.com

I own a Dreamline. I installed it during a major renovation in 2014-2015. It has been used every single day, and has had no problems at all. The Pros: It is stupid easy to keep clean. No grout lines to harbor mold or mildew. The walls wipe down with nothing more than a damp sponge. If you apply a hydrophobic coating to the glass, the water just beads and runs off. I use a squee-gee before stepping out, but that is just a personal preference. The floor is just as easy. A little bleach water and it stays brilliant white. The Cons: You must have a square and true enclosure to set it into. Easy with metal studs; less easy with wood. You only have 1/16ths forgiveness to align the three panels properly. Take your time, and use your six foot level often. It is designed as a direct-to-studs installation. Up to you if you want to do that. Too risky for me, though. I created a water-tight box with cement board and RedGard. Added a bit of time and expense, but now I have a layered defense against water leaks. The pan instructions say that setting it into a mortar bed is optional. I recommend it. You want a rock solid floor. Without mortar you can feel the pan flexing as you walk on it. And flexing can lead to cracks down the road. LPT: Cracks are very bad ju-ju. Use quality shower fixtures and hardware. Not included in the kit. You have to provide it. So get stainless steel or brass. You don’t want to have to pull this apart for stupid reasons. More on reddit.com

Are they secured to the wall or do they move ? If secure fill all those gaps with 100% silicone , no caulk as caulk molds. Use tape 1/4 out on both sides of each gap, fill them and run your gloved finger over them to make smooth. Once done peel tape to make clean lines. More on reddit.com