I just did the same 1x9 conversion to my 2019 Trek Marlin 7 over the summer that was done in that video. It cost about $60 and I have no regrets. I know my bike and riding style are different but we both have Acera groupsets and I'm weighing upgrading the rest of the drivetrain vs upbiking. I suspect the OP may be as well if he's talking about going to the LBS. Here's my impression:

- narrow/wide chainrings solve chain drop but not ghost shifting, that's a RD or cable adjustment issue or a bent derailleur hanger.
- a 1x groupset appears to have less friction in the mix
- the narrower the range on the cassette, the less wear and tear on the chain

Barring drilling out the rivets it's a no-risk conversion if you can swap in another square taper compatible crank with bolts from a co-op. That's what I did by stripping my old bike of its crank. There is a financial investment but I did it for about $60. I also kept all the old parts in case I want to try to do Trek's buy-back program and go with a newer model with many of the features I've wanted to upgrade now being stock.