Your description of the 3800 reminds me of what I think of as the first generation 3800 from the 1970s. The second generation added support for IBM's version of page printer support, and has been replaced by other printers, most notably, the 3900 printer as well as a number of sheet fed printers, all of which use the PSF utility to operate the printers, with JESx not completely in the loop. The JES2 code to support first generation 3800 printers was complex. I'm sure similar updates to JES3 were equally complex. The code to support the new printers was far more complex, possibly to the point that JES2 (or possibly it was JES3, I don't know what IBM politics were involved here) did not want to do this code, which led to PSF and the code in JES2 and JES3 to interface with PSF.
In the 1980s I went from a 3800 shop to a non-3800 shop that went to Xerox printers. I was never real impressed with Xerox printers, though they mostly worked well once one sort of understood the mysteries of the DJDE command language. I remember coding a nasty JES2 modification that threw a DJDE ahead of the JES2 separator page to force two logical pages on one physical page, put the printer in duplex mode to print on both sides of the paper and start a new physical page. At least that shop didn't have any first generation 3800 stuff, much less (fortunately) any second generation 3800 stuff! I remember doing the mod, and some of the issues I had doing it, but I have zero memory of the contents of what I sent to the printer.
What little respect I had for the Xerox printer evaporated when I found that Xerox's claims that the printer supported all 3211 command sequences turned out to be a lie. The problem was the method JES2 of that era used to translate ASA carriage control the machine carriage control sometimes produced extremely strange command sequences that the Xerox printer did not understand. I proved this by using GTF CCW tracing. Xerox (around 1985 or 1986) had zero interest in correcting this problem, though for all I know it's been fixed by now This problem was resolved by writing the data to tape (it was quite a lot of data) and running it through a utility I wrote to translate ASA carriage control to machine carriage control, which bypassed the JES2 code.
I think your shop is going to have to remove the OPTCD=J stuff from your applications and write the Xerox command stuff in its place. It makes me glad I'm retired!