Is this RTA forgiving when it comes to wicking when you take out and about, and it's rolling around, upside down in your pocket?

IMHO it's totally safe.
I have 2 of the ByKa v.8 YFTK and they are safe as any other ByKa can be for handling (and they are almost legendary for that).

In many weeks of use (and many different building/wicking configurations) I only managed to make it leak once because I overdid the cotton "tails" thinning of an already smallish 2mm. diameter wick AND the atom was later left on the car's cockpit in a very hot summer day (heating of air in the half empty tank, hence overpressure).
In other words, in over a month of daily use, it only leaked once and mostly for my carelessness

Thanks for the reply. I was just about buy a Kayfun v5 again, because I sold mine and miss it. How does the V8 compare to the Kayfun 5?

Well, we are talking clones here, both the YFTK BY-Ka v.8 and the Coppervape Kayfun 5 clones I have should be good clones that vape and behave very closely to the originals (IMHO, at least... and I have also original BY-Kas 6,7 & 8).

I have a nano and a standard YFTK v.8 - the nano is my daily vape since nearly one and a half month - and since I vape strong natural tobaccos I refill/rewick them at least twice a day and rebuild them nearly daily, so they are used and disassembled quite a lot.

As said I vape almost exclusively naturally extracted tobaccos on the BY-Kas in a quite airy MTL (nano with 1.4mm air insert & standard "long" with 1.7mm air insert) and sweet, creamy or fruity stuff in a "flavour style" on the Kayfun 5, where I never used any "MTL kit" to choke it down.

While I do enjoy the "swiss watch precision" vape of Kayfuns, I noticed that they are not so aromatic for tobacco extract (I never tried to mod the KF5 with the kit to a "proper MTL" style, but had the chance to test it from a friend and the ByKa v.6 I was vaping at the time was still superior with NETs).
I also used a Kayfun v.3 Mini for tobaccos, and, while enjoying it, I still find the BY-Kas were superior for their aroma rendition.

All in all, you will very probably enjoy the BY-Ka, of which the v.8 is the latest and probably the best iteration so far, as it can be assembled with different choices of air inserts and nano or standard chimney/tank to vape it from a very tight MTL to a quite airy flavour style vape (2.3mm. air insert and 2.5mm. coils in the 0.6-0.8 ohm range)
When properly coiled and wicked to your liking (an easy thing to achieve in just a few tests) it will give you a very fluid and smooth vape just like Kayfuns, and the ByKa reliability and sturdiness - the YFTK clones too - are top notch.

For what is worth, I noticed that on the forums there are complaints for the PC tank of the YFTK (tank's material is better and tougher on original ByKas than on YFTK) and some complaint about whistling with a single airhole open, but - lucky me! - I never experienced any of these on my v.8s.

Sorry for the lenght, and - of course - all this is only IMHO. :-)

I don't know if the tank material is exceptionally weak with the YFTK clone or not, but the tank for sure is exceptionally air-tight with the LFC screwed all the way down. If you fill it up too much and leave no room for air to compress it's strong enough to pop the plastic tank insert. That's what happened to me.

The wistleling with the outer afc closed down I would more or less ascribe to user error. In the stream of air the air is fastest when it passes the narrowest point. That should be just below the coil. Fast air at the outer afc produces a whistle.
That whistle is easily remedied by putting in a smaller deck insert while leaving the outer afc closed or even opening it up a bit. I always leave mine completely open and for me it's one of the smoothest and most silent RTAs out there.

It's a fantastic RTA, which indeed likes darker flavour profiles like the Hussar RTA or the UTA v2 do, while also being a bit more suited to brighter stuff than those two.
Shame that YFTK don't offer replacement tank inserts!