I am experiencing multiple issues on my iMac desktop

recently i had cause to reset my 2017 iMac to factory settings, and reinstall everything i needed. i was really looking forward to a lean, mean, computing machine. but i was cruelly disappointed. so many problems. here are just the Desktop ones. i'll number them for ease of reading.

previously this machine was running OS 13.0. now, and this was not my choice, it's running OS 13.6.9. this may or may not be relevant, as may the factory reset itself.

1. unexplained differences between user accounts

there are three, one admin a/c, and two user a/cs. on this (user) a/c, the one i use most of the time, and only on this a/c, on the Desktop, disks appear with their disk size and free space. this has never happened before. presumably there's a setting, as there are instances where it is set off, but i'm ****** if i can find it! i certainly never set it, and i'd not do so as a choice.

2. things moving around on the Desktop

i put things where i want them to be for ease of use, as i'm sure everyone does, but for me at least, Apple keeps moving them around! it's beyond irritating! why does it do it? can it be stopped? if it matters, it also only happens on this user a/c, and it only happens with disks and servers etc, not with files and folders. but i only have disks and aliases on my Desktop.

loss of Menu bar

3. the secondary monitor has lost its menu bar, again in this a/c only. i need it back, please. help! not sure if this is a Desktop problem, but it certainly effects it. i've tried logging out and back in, i've tried a Restart, and finally i've tried the old swictch it off and on again method. nothing helped.

thanks for reading.

[Re-Titled by Moderator]