Two user accounts, one guy. Merge possible?

Since you have an Apple Silicon M4 MacBook Pro and have had to erase and reinstall macOS, I would first establish which of the two accounts contains your original data, settings, and preferences before deleting either one.

1. Understand the Owner account versus an Administrator account

On Apple Silicon Macs, there is an important distinction between the Owner and an Administrator.

The Owner is associated with the Mac's security and startup policy. The Owner role is normally established during the initial setup of the Mac, and it is not simply another name for an Administrator account.

An Administrator can ordinarily add and remove user accounts and change account privileges. 

However, certain security-sensitive operations on Apple Silicon Macs may require authorization from an Owner. Having administrator privileges does not, by itself, guarantee access to every Owner-authorised operation.

Apple's documentation explains how to set up and manage users and groups:

• Set up users, guests, and groups on Mac — Apple Support

• The perils of M1 ownership — The Eclectic Light Company

• Ownership means two different things in Macs — The Eclectic Light Company

2. Before deleting the duplicate account

Because you have two accounts, Me and Me_1, I would not delete either account until you have confirmed where your valuable data resides.

First, log in to each account separately and compare the Documents, Desktop, Pictures, Downloads, application settings, and other important files. Also check which account contains the preferences and configuration you want to preserve.

Make sure you have a current, verified backup before proceeding.

3. If you decide to remove Me_1

Apple's official instructions are here:

Delete a user or group on Mac — Apple Support

On your Mac:

1. Open Apple menu > System Settings > Users & Groups.
2. Click the Info button beside the account you intend to remove.
3. Select Delete User.
4. Carefully review the available options for handling that user's home folder.

If you want to preserve the account's files, choose Save the home folder in a disk image. This archives its documents and information in /Users/Deleted Users/. Alternatively, you can leave the home folder in place. Do not select the option to delete the home folder unless you are certain its contents are no longer needed.

You must be logged out of the account being deleted.

4. One important caution

Deleting Me_1 will not merge its files, preferences, or application settings into Me. If the account you want to keep is missing important data or settings, those may need to be transferred separately.

My recommendation: Preserve both accounts until you have identified which one has the original data and which one has the correct Owner and Administrator privileges. Once that is established, you can decide whether to remove the duplicate or transfer the missing data and settings safely.

When you did the reinstall you should have been offered the option to recover from a TM backup before you created the new user - or to merge them if they had the same name. If you'd done this then you wouldn't have had any problems. I think it would be quicker to do the install again rather than trying to fix things piecemeal.

Just because an account has the same name it doesn't mean that MacOS will recognize it as the same account and transfer ownership and access rights across. Ownership & rights go with the user ID; an account can have the same name but a different UID from the account you transferred across from and therefore won't inherit rights. You might be OK but if not and you have files in a User account which doesn't own them then you are probably going to get very familiar Terminal and the 'chown' command.

Now, let me add, the reason Apple Support had me reinstall was some incidents of shutting down overnight (when I'd left it in sleep mode), intermittent keystroke lags (fixed by rebooting), and Mail freezing overnight, and needing to be force quit in the am.

So, maybe that was user related?

And merging my Time Machine/original user account with my newly made Me_1 may not be in my best interests…

I was offered the TM backup as a recovery disk. And I chose it. Nowhere was there any mention of users. And it was a slog to reinstall, so I'll not be repeating that in any likelihood unless absolutely necessary.

Yes you can have 2 Admin account

But only one " Owner Account  " which usually very first Account used when the Computer was Very First Setup as New and out of the box.

Adding additional Admin Account can be done there after.

There is an important distinction between the Owner and an Administrator on Apple Silicon Computer as covered in previous links .

Original date is in Me_1, also the admin account