Herpes can be transmitted through contact with skin showing no symptoms, outside of the area protected by the condom, such as scrotum, vulva, perineum. How do providers protect against that, so that I know it’s safe to engage? Antivirals can help but they’re no guarantee. This makes the risk of contracting something quite high for both.

You can lower your risks by:

your choices are
(1) sex with yourself  
(2) sex with a robot/doll
(3) sex with a monogamous partner

The fact that risk exists does not mean it is “quite high.”

you're asking if you should jump off a tall building.
Take the leap or stay on the ground!

Sex with multiple partners is a roll of the dice.....don't overthink it......if the concerns you have over shadow the anticipation---back off.....one way though to help minimize your risk----eat the pussy and the ass....if something is amiss you will likely spot it if you go in close----before your insert your junk....covered or not covered!!   What you are doing is actually a careful inspection----the gal will presume that is the way you roll to get into it ---don't ask----just go  for it......won't be her first rodeo.......like inspecting a Cantaloupe---thump it to see if its ripe !

Nothing is without risk. But I've been playing this game for decades and never caught a thing. So stop worrying or get a different hobby.

I have "Hobbied" before the name "Hobby" became prevalent---various places around the world and most of the United States---I have never caught anything ....except......there was this super cute gal in the office-----we were working on some reports on a Saturday---no one there but us---I noticed her tight jeans and tight ass along with her bright yellow top with her nipples sticking out when she came in to assist with the reports.....one thing led to another----and next thing I know we were linked up in every way possible----on her knees providing one of the most magnificent BBBJ's ever and since----more kissing---the top came off-then the jeans---no panties----and I found myself compromised---the dick went in unguided....apparently she had done this before !!!   A couple days later I had an odd sensation in my penis and nut sack----not long after the first of the odd sensations---a discharge began to form....Wow......Terror set it----called the Urologist for an emergency appointment----couldn't see me until the next morning.... sleepless night followed--next morning I was there before the appointment time---Doc checked me out and asked if I had gotten any strange lately?   Had to tell him what happened---sparing most of the details-----got a prescription and was just fine in a few days........So......point is----you are likely at greater risk with a civilian gal than an escort----unless you cruise the truck lot at Pilot for a Lot Lizard!!!

What about the girl from the bar you take home? You don't know her testing status and more likely than not she isn't recently tested.

Full  
Body
Condom

I hear this all the time. Risks are higher w civilians. Sure maybe amongst the general population and maybe world wide.  But in the same conversation I see “limit number of partners”. WE don’t do that by very nature of the business.
I have often wondered about either one of the HSVs.  Would a person that makes a way better than average living suddenly go back to reality if they contracted it? OR would they manage it and let the good times continue?
But yeah there’s a risk. For me it’s better than a side chick!
Be safe!

How can you swim without getting wet ?

I hear people at work talking about all the apps they’re on, meet people for “hook ups “ no protection , everyday a different date, new app new person. No protection “ oh he or she looks nice “ yeah , no.  
I wouldn’t . Stay safe use protection .

just as you suggest to no more than two at a time.  So far, it's working.  

Two is plenty  
Three’s a crowd
And four is too many!