How about I tell you what I have done and see if its something you may want to look into. Needless to say, when I retired the last thing I wanted to do was computer upkeep of endless programs, storage, etc. So, I ended up looking at Chromebooks and settled on 1 that was was from Acer. I have the Acer Chromebook 11 which I purchased from Amazon at around $200- 250 ish. Let me tell you why.
First off I have minimal storage so If you need to save anything it can be done online at google(mygoogledrive--their version of the cloud) OR what I do for personal information is to use a thumb drive(aka as a flash drive) that just plugs into a usb port(computer has 2 usb ports). Do you have a gmail account? Its free so you can also keep using the online email you already have through the internet via the Chrome browser. All the programs you will use are maintained and updated via google and they take care of all of that for you.
Next like you, I wanted a wireless keyboard and mouse and separate monitor(big one).
I got my monitor at Best Buy and it is a HP 25es and got it on sale for around $100.00 If you already have a wireless mouse and keyboard those should just be plug and play with little to no intervention from you. So I am sure you are wondering how to put 3 separate devices(not monitor) on a computer with only 2 usb ports? I got one extended usb device that has multiple places to plug in up to 4 usb devices.($10 or under at walmart) and put the keyboard and mouse on that one, leaving the other one for the flash drive or anything else I may want to use there.
The monitor you get should be HD and have the HDMI port on the back of it and it should come supplied with the cord for hookup. The back/side of the Chromebook has a place to plug in both HDMI and the old style VGA monitors.
Well this post is getting long so take a read- ask questions, etc. LOL