Jerry,
Who makes the best locomotives? That is such the loaded question lol. If you think asking "Brexit - pro or con?" starts arguments, go to a US forum and ask which manufacturer of US locomotives is best lol. The calculus not only depends on make, but also vintage. Broadway Limited, Bachmann, Atlas, Athearn, Walthers (Proto 1000 and Proto 2000) all have their own fans and detractors.
In addition to various U.S. forums, you may want to explore the British division of the National Model Railroad Association (NMRA).
https://www.nmrabr.org.uk/latest-nmra-news/387-nmrar-2018-convention-announced
Joining the NMRA has proven to be very beneficial. My local division, while small, has a number of very knowledgeable persons willing to help and going to our region convention has provided great learning experiences, both from visiting layouts and attending clinics.
For vehicles, perhaps Classic Metals Works is the most popular and Oxford is starting to make 1/87 vehicles.
I hope this provides a good starting point for you.
Dave