My MTB is a single speed but not a fixed gear. IMO a fixie makes no sense off road. I’m sure there are “purists” out there that would swear by it but I like being able to put my pedals where I want, when I want. Plus, which such low gearing I’d likely blow my knees out on the descents!

Yes, SoCal is baked hard. Here it’s all sand and clay. I took a nice low speed spill on a climb when my front wheel dropped off into a deep rut. I landed on the sandy soil on my hands and knees and it felt like I was flopping onto the bed ;-)

Because I like my water icy cold, and coldness makes condensation which collects lots o’ dirt, I used to make sleeves for my water bottles from, well, sleeves from old sweatshirts. I’d run a drawstring thru a hole in the knit cuff, cut off the other end at an appropriate length and sew it up. Took 5 min to make two.

Then, at some point in time, I switched to a CamelBak most of the time.

I laughed when you said “relatively soft” ground. In SoCal the most technical parts of MTB rides are usually on rocks.