8GB of RAM is fine for your needs but I'd get 16GB as these machine cannot be upgraded after buying. NEVER EVER buy less storage than you already have! So if the old machine has 512GB then buy a new 512GB (or more) model.
Trackpad or mouse, is totally personal preference. I like using the MTP but many many others prefer the mouse.
By the way, did you know Apple has 12 month same as cash financing? When you contact Apple's online store ask them about this!! I've done this several times and just set up my bank to send 12 equal payments and 1 year later it's paid with zero interest.
When you make your decision, make a Time Machine backup of the old machine, refer to Back up your Mac with Time Machine you will need an External Hard Disk and I would suggest the OWC Mercury Elite Pro. Backblaze is worthless for migrating to a new machine, in other less blunt words it simply will not migrate to a new machine whereas Time Machine will. If you don't heed that advice you will NOT be happy. Regarding migrating to the new machine, please read the advice below for migrating:
When you buy a new Mac the easiest, quickest and most reliable method to migrate from the old Mac to the new Mac is to simply connect the old Mac's Time Machine External Hard Disk to the new Mac using a USB cable before you turn on the new Mac. You will likely need a USB A to USB C adapter, you can find them on Amazon for $10 or less. When you start the new Mac for the first time it will startup Setup Assistant (SA), SA will get to a point where it asks if you are migrating from another computer, select Yes and follow the on-screen prompts and it's done! It is THAT simple.
If you have already done SA on the new computer then simply connect the Time Machine External Hard Disk using a USB cable and launch Migration Assistant (MA) which is located in Applications - Utilities - MA. Then follow the on-screen prompts.
The ONLY difference between MA and SA is MA will create a new user account that you need to log into.
Both SA and MA migrate applications (not 32 bit apps), data files & settings. They do not migrate Mac OS itself. Some professional apps such as Adobe and Microsoft apps may require re-installing their apps as they will not allow them to be migrated. As long as you kept the security keys for installing their apps, it is not an issue.
Finally, never EVER use Wi-Fi when doing Setup Assistant or Migration Assistant. Why, it simply fails in most cases. Please read and follow the directions in Setup Assistant and Migration Assistant. If you do not have a Time Machine backup of the older Mac then create one! If you are not aware of Time Machine, please read Back up your Mac with Time Machine and finally if you need an External Hard Disk to use as a Time Machine External Hard Disk then many experience users on these forums prefer the OWC Mercury Elite Pro due to it's reasonable price, high level of quality and ease of use.
By the way, I'm 69 and on a fixed income too.
