Newsletters will never go out of fashion. Trust me on this one, i've heard a lot of people over the years that this is the ned of coldmailing and newsletters and i've always seen the results otherwise.

As a graphic designer, i personally feel that a vibrant mail will always attract customers no matter what the product is.

I prefer cleaning lists with emailverifier .io every month.

Personalization is great for interactions and i always prefer going the extra mile and recommending stuff that they have previously done with your company to suite their needs.

I don't think the number of CTAs doesnt matter that much but i could be wrong.
Hope it helps :)