I would never try to write a review for it as I don't have the "Chops".
If you could write an essay that got at a B, you can write a review. Follow basic good writing practice.
Tell your readers your background and likes and dislikes.
Explain how you felt using the product was. Be honest, but try to avoid outright negativity.
Avoid damning with faint praise, if you didn't like something, be clear, but also if it's something subjective, be clear that it is, like "I prefer buttons/sliders/rotaries/touchscreen/app on phone for volume (delete as appropriate) and this used my least favorite option".
Be direct if you liked or disliked a sonic trait.
Keep it simple, less words are more. Avoid flowery vichyssoise of verbiage and empty wankwords and wank phrases.
It is difficult to express sonic performance in words, but there is relatively standard terminology, I remember from my reviewer days a general cribsheet of "audiophile terminology", find it, use, refer your readers to it as reference.
I would avoid making 70% of the review copy & paste from the manufacturers literature, refer peeps by link. Instead try to bring out what makes the device unique (if anything) compared to other widgets.
If you do a video review, that's harder. You must be able to project across the fourth wall, scrips are pretty much necessary (I'm totally sh!te doing ad hoc at least) and you need to be entertaining to keep peeps watching.
That's tough sh!t, if you do it well though you can monetise pretty big on u-toob and other sites and afford to be honest and independent.
Thor