I have read elsewhere, that among all the things Glock does really well, one thing they don't do well is make reliable 9mm 10 round full size mags. Of course if it is just a plinking gun it probably doesn't matter.
I voted for G26 mags but it occurs to me that unless they are less reliable (as someone alluded to but I don’t know), G19 ten round mags might be easier to change magazines quickly should the need arise.
Where do you get this information? If you “read it” somewhere it tells me you have no experience with them. If you have no experience with them perhaps you should refrain from commenting, no?
The problem, and only problem, I have found with Glock factory 10 round magazines (I own a bunch in G17, G19 and a few G26) is that the G17 and G19 mags are hard to load the last 1 or 2 rounds into them when they are new. After a while the spring tension is a bit less and easier to load. The 10 round G26 mags are easier to load. All Glock 10 round mags, in my experience, work very very well.
You will find that in California G26 mags are harder to come by and rarely go on sale, but G19 and G17 Glock mags can be found on sale more often.
Personally, I stick with Glock factory mags because they are reliable and have no real experience with Magpul, ETS or other brands.
Something I did learn with my PC Carbine that could have been a problem was I used an old beat up Glock 19 Mag a buddy gave me. The mag lips were spread a bit so rounds would hit just below the feed ramp on the carbine barrel. One round smacked so hard it forced the bullet back into the case. Luckily when it did that the round popped upright and the gun jammed. I found out later it was a mag that he had used for years and was worn out...Duh...
Anyway, regardless of what mags you buy keep an eye on the mag lips when they get older so you don’t have problems.
Regarding red dot sights;
I bought a Sig Sauer Romeo 5 for my AR and liked it so much I got one for my PC Carbine. If you use the taller mount you can use the red dot and still use the iron sights as well. Pretty neat.
Have fun with your PC Carbine. I really like mine. It has become my favorite long gun.