If you dilute e-liquid that contains nicotine with CBD e-liquid, then to be on the safer side of things you should avoid vaping it too long after you mix the two together. AFAIK a slow chemical reaction tends to occur after adding nicotine to cannabinoids like CBD and terpenes commonly found in CBD e-liquid. Especially when it comes to the wide variety of terpenes that are typifying of "broad spectrum" and "full spectrum" CBD products, this could cause side effects that may potentially become harmful with prolonged use. In fact, a lot of terpenes haven't been well studied, their long term effects on health still remain largely unknown to date, and, a typical (legal) "broad spectrum" CBD product can contain more than 100 different terpenes so, there's always more than several terpenes in there that do not belong in the "generally recognized as safe" category. (Maybe one day they might all wind up in that category, or they might not... at least for now, it's mainly about speculation, no matter the fact it's legal, as the process of lawmaking isn't synonymous to the scientific method of course.)
Manufacturers of CBD products are very often trying to mislead with marketing descriptions like "whole plant" or "natural". The reality is that the purest (and safest) type of CBD is called "pure CBD isolate", which is both 1/ expensive and 2/ not exactly very potent due to lacking what is known as the "entourage effect" from all the various terpenes that, although they vastly help to improve the potency of CBD as a result from this effect, might not be equally as harmless as pure CBD isolate. Needless to say you also need to 3/ factor in how pure is "pure", as there exists no linear relationship between, e.g., "99.6% pure" or "99.7% pure" and the level of harm that may be caused by each different type of impurity.
I've used CBD products myself, regularly for more than a year, in the form of sublingual tincture and in the form of vaping CBD e-liquid, also including fairly high strength (600mg CBD in a 10ml bottle of e-liquid) diluted with regular e-liquid at 3mg of nicotine strength in an RDA, that I vaped on a single battery mech mod at 0.11 ohms dual coil, and that, with the battery fully charged, translates to ~129 watts after the voltage sag of the battery. To be more specific, I was using loudly crackling 27/36 Ni80 alien coils at 5 wraps 2.5mm─same specs as the ones that Mike (m.terk) also sells on his website BTW─in the 25mm Kennedy RDA, a typical flavor chasing setup the flavor quality of which IME is nothing short of exquisite. Using Cotton Bacon 2.0 the way I have described in my 2nd reply to this thread and getting no burned taste of any kind, abeit I am well aware that can still happen if I try to wick it up too impatiently, in which case it'll only get
MORE time consuming because,
THEN, I just end up having to redo it yet again thinking that smoking normal cigarettes was so much less of a PITA...
That being said, I stopped using CBD altogether after I switched to using dōTERRA Copaiba (Copaifera) Essential Oil, that can not (!) be vaped, but that can be used as a sublingual tincture if using not (!) more than 6 droplets per day. 1-2 drops per day is usually sufficient for me, which means that I use less than one 15ml bottle per year. The main important ingredient is β-caryophyllene, a natural cyclic sesquiterpene that is generally recognized as safe.