My $100 mistake
I took my dentist’s recommendation (see the OP) and bought an electric toothbrush. This one:
Oral-B iO rechargeable electric toothbrush:
https://a.co/d/4onMsIe

After using it for more than two weeks, I considered it to be a $100 mistake. There were three things wrong with it:

First, its little round brush head wouldn’t hold much toothpaste. It’s mostly gone in less than a minute.

Second, its body, essentially round in cross section, provides no tactile clue as to how the brush bristles are oriented. The side or back of the brush head was often banging against my teeth.

Third, its round, smooth body has poor traction. it’s slicker than boiled owl shit after saliva and toothpaste cascades over it. With its significant weight, it’s prone to slipping out of my grasp. (I lean over my wash basin while brushing my teeth. Else saliva and toothpaste dribble over my shirt and counter.)

I just didn’t like the damned thing. So, after some research, I bought a different electric toothbrush to replace it. Another Oral-B model. This one:
Oral-B Pulsar Battery Toothbrush, 2 Count. $10.99 ($5.50 each)
https://a.co/d/6D9eF2O

It’s a much better toothbrush, and it’s much less expensive to boot. It has none of the three problems of the Oral-B iO:
* Its oval brush head holds more toothpaste.
* Its asymmetrical body provides good tactile orientation info.
* Its body has LOTS of texture for a good grip. With its much lighter weight, there’s no slippage at all.

Its battery is integral – not replaceable. When it expires you buy another toothbrush.

“OMG! How uneconomical,” some might say. Well, maybe not so. Looking at its reviews on Amazon that I judge to be credible, its battery life is approximately three months.

Furthermore, the brush heads of the rechargeable Oral-B iO have a recommended replacement interval of three months. And, the Oral-B brand brush heads are expensive:
Oral-B Brush Heads, 2 Count: $24.95 ($12.48 each)
https://a.co/d/efewY82

Twice as much as the Oral-B Pulsar! There are off-brand brush heads for the Oral-B iO that are less expensive, and might be fine.

But I’m sticking with the nifty Oral-B Pulsar. It makes brushing almost fun!

I'm fine with a manual. I get a new one from my dentist everytime I get my teeth cleaned.

quote:

Oral-B iO rechargeable electric toothbrush:
https://a.co/d/4onMsIe

After using it for more than two weeks, I considered it to be a $100 mistake.

Interesting, because I haven't encountered any of these issues. I had to go look at mine, and the box it came in, before I discovered the difference.

I have the Oral-B Genius X. I never even occurred to me that there would be so many differences between models. I got mine at Costco for about the same price that you paid...although I did get two handles, brush heads, chargers, and travel cases.

1. You're right about the brush head not holding much toothpaste. I believe the brush was intended to be used without toothpaste as it doesn't need the abrasive action of the paste to clean the teeth...I use a rinse before brushing. Without toothpaste and closing my lips around the brush seems to prevent dripping.

2. The Genius X is body asymmetrical , but even if it wasn't, you'd only have to align it with your teeth once and guide it alone your gum line...allowing the action of the motor to work.

3. The Genius X has a soft texture along the two flats on the side away from the brushes which give excellent adhesion

Obviously YMMV, but careful selection between models may produce more desired results

^^^^^^
Re: “Obviously YMMV, but careful selection between models may produce more desired results”

Indeed. The Oral-B Pulsar was the result of my careful selection between models.

Oral B, 3 dental visits a year, buy replacement heads off eBay.