Managing Eurail pass is confusing

I'm linking the Man in Seat 61. He might have the answer. I have never used a Eurail pass, but one of the things I know about it is that it's generally not useful for a short trip like London-Oxford.
https://www.seat61.com/how-to-use-a-eurail-pass.htm

For any UK rail journey a seat reservation is free of charge- you can make them at a staffed station or there are a couple of ways to make them on line. There are no UK rail routes where a reservation is required, although some where it is advisable, and many routes where they can't even be made- just hop on routes. Oxford to London is a route where you apparently can make reservations, but very few people do.
I, too, wouldn't use a pass day to Oxford, just buy point to point tickets. But I would use a pass day on London to Edinburgh as an example- in that case make a free reservation on LNER's own website.

I'm used to inter-railing (as we call it)/eurailing with paper tickets, not apps so that side of it is beyond me. On paper tickets you just write your journey on the back pages of the pass- very easy!!

This thread from a few years ago might help. I think you go to the ticket site and start as if you are buying a ticket but then you have an option to reserve a seat or a bicycle space. https://community.ricksteves.com/travel-forum/england/britrail-passes-and-reservations

Hi David, If your pass is unused and hasn’t been activated, Eurail says you can submit a refund request. If you keep it, I recall activating the day before I was going to use it. I went through a lot of this same stuff you’re mentioning a couple of years in a row ( figured I’d give it another shot…) I read everything Man in Seat 61 had, etc. I did the math beforehand and I would indeed save money. Long stretches between different countries or last minute jaunts can be worth it. This year there’s no way in the world I’d use one. There were glitches that were maddening and customer service was often unreachable when I most needed it. I’m extremely comfortable booking trains through various sites, etc and I felt my IQ was knocked down 50 points dealing with my Eurailpass. I wish I could be more specific, however I think I’ve blocked it all out for self-preservation. When it’s good it’s very good, and when it’s bad…..

Thank you for the helpful replies everyone. I did indeed find the answers I was looking for on seat61.com, especially for managing a set of family passes on one phone and how those work with trips and reservations. I'm copying the relevant parts below for anyone else that comes across this thread in the future with similar questions.

#1) See the overall guide for managing your mobile pass for the answers to this one.

#2) Passes vs. reservations:

Listen up, as this often confuses people! The process of (1) activating and using a Eurail pass, and (2) making seat or berth reservations on particular trains to go with your pass, are two entirely different, separate, unconnected things. One does not affect the other, in any way at all.

When you find a train in the Rail Planner app, add it to your 'trip' then add it to your pass, this does not reserve seats or 'book' that train in any way whatsoever. All it does is make the pass valid for that journey. It's simply an electronic record that helps Interrail management allocate pass revenue between operators.

Similarly, making a seat or berth reservation on a particular train does not in any way activate your pass or use up a day on your pass or even commit you to using the pass on that train or date. If you have to enter your pass number when reserving, that's only to stop people without a pass making a reservation, it does not affect, trigger or use up your pass. Reservations will not magically show up on your pass or in the Railplanner app, even if you had to enter your pass number when reserving, because your pass and any reservations you make are entirely unconnected, separate things.

The pass itself sits in the Rail Planner app on your phone. A seat or berth reservation (depending how it's made) might be an email with QR code shown on your phone or printed out, or a QR code shown in a train operator's app, or a hard copy ticket from a ticket office. It's not connected to the pass in any way (did I mention that?)

It's just that you need to be in possession of both a pass (properly set up for that train) and a valid reservation before boarding any train which has compulsory reservations. A pass alone is sufficient for most local/regional trains or for trains on which reservation is optional.

—Source

#3) Managing trips for multiple passes on a single phone

The process for handling multiple passes on one phone is a bit clunky, but works. If you try to add a 2nd pass to the same trip, it offers to duplicate the trip. Go ahead and create a duplicate trip for each person in your group and connect their pass to that trip (remember to rename each trip so you know which trip belongs to which person). When you find a train in the journey planner and want to save it to your trip, you are offered tick-box options to save it to multiple trips, so you can save it to everyone's trip at once. When you board the train, you need to open each person's trip and add that journey to that person's pass - unfortunately there's currently no way to do that in one go!

—Source

For #4, the only reservation I think I'll worry about is London to Paris which I already have.

Overall, I'm not sure if it was the best idea to purchase these passes. I probably could have saved money if I had just purchased point-to-point tickets. Especially since the only trip that crosses borders is the Eurostar from London to Paris. Lesson learned I guess! To console myself, I'll just look at the really expensive Eurostar tickets and pretend that those were the only ones I would have been able to get.

Well done, David and beautifully explained. You brought it all back for me. Only once did a conductor insist I prove that I had deducted the day from my travel days. I had a couple of spotty wifi moments that were challenging and I think I used screenshots as a backup...? Safe travels