Regarding calibers, yeah, I've thought about that. I mean I haven't put a lot of thought into it, but more notice unusual calibers and be like "how the hell did they come up with that?" or "why couldn't they just round it off". Particularly for many of the "old school" cartridges and calibers. I assume the modern cartridges are a balance of many factors and assisted by CADD and other software. So there are times I wondered ho wor why they came up with some of the calibers over 100 years ago.
Some have actually very explanations, like the 7.92 Mauser, which is probably the world most popular military cartridge. No Inspector, your beloved .22 lr does not count.

Anyways, it is my understanding that it started as 8 mm, but then tweaks and bullet size and rifling and barrel profile considerations then "factored" in.
For optics, particularly the reasoning for LPVOs ranges, there are many articles about them online. Look up discussion on the Nightforce NXS and ATACR lines. I think on Sniper Hide or another, there are a few threads where one of the leads from Nightforce in the development of those lines explains the considerations and limitations.