Chiming in, sorry if this has already been mentioned above.
1] Reviews are very open ended, some include gritty details while others are very generalized. Try to read through the thread for other clues if it isn't clear on who the OP is reviewing. The four numbers, is the last 4 digits of the contact phone number. If you are unsure of who the review is about you can feel free to ask in the thread for clarification for sure and sometimes some people will share the link to the ad that way.
2] PERB is more of a forum, versus Leolist.cc and Tryst.link, those ones have better filters for narrowing searches. Tryst is the absolute best for filtering, you can pick by hair colour/body type/keywords etc. On Leo I would search words like slender, petite, spinner, pint sized, fun sized, pocket rocket, skinny, thin, lean, sinewy. Think of it like, how would you as a thin woman describe yourself in an advertisement? Personally I would start with Tryst as there are way less fakes to weed out. Also read your other posts and I'm fairly certain the USA based IP addresses block the photos on Leolist which is unfortunate

if you need pointers on terminology there is a stickied post in the Lounge area.
For an advanced search, when you use the search tool, click the settings button for an advanced search where you can filter keywords on posts by date.
3] the only times I've seen filters for services are on agency websites, for example Asian Fever comes to mind. As a rule of thumb a GFE experience generally includes LFK, covered or bareback BJ, multiple positions, and daty. Anything beyond that, I would just ask the provider directly what services they offer, and how big the YMMV factor is for them.