Hiya
I'm not sure I'd be suggesting PUPD in this case - not because I think he's too young (though it is in general recommended as a last resort after consistently trying shh pat with an appropriate routine, and ruling out other causes e.g. hunger) but because genuinely at this age I don't think a dreamfeed, then a 2am feed is unreasonable. Sorry I know that's perhaps not what you want to hear though! PUPD is generally used to break a prop such as feeding to sleep or rocking (he sounds like this isn't the case?), and won't work at all if there is a genuine reason for LO to wake.
My suggestion would be to try far less stimulating ways to get a resettle - PUPD is super-stimulating and really not what you want in the middle of the night unless you have to - so perhaps putting a paci in (if you use one), or using a variation of shh pat that you and LO find more acceptable. My DS used to like his head being stroked and a hand on his tummy
In general an easy resettle using one of those means would suggest the waking isn't hunger, but given a 4h stretch is not an unreasonable gap between feeds for a 4 month old, if LO struggles to go back off or wakes again after 15-30 mins I would suspect hunger and feed. You may find a quick feed at 2am gets you all back to sleep more quickly and then one of the resettling tactics will work more easily at 4am
STTN is a variable process, and not all LOs are ready for a long stretch at this age. I know it's exhausting but it won't last forever!
As ever though - the choice is yours
In response to the specific questions - provided he is still safe to be swaddled (not rolling), I wouldn't unswaddle him. That is only going to wake him up and stimulate him more - totally the opposite of what you are trying to achieve. PUPD at this age involves much more settling in the cot than picking up, so is part of a continuum with shh pat rather than being a separate thing entirely. I would leave him swaddled and try to 'do the minimum' in terms of intervention, soothing in the crib as far as possible. You could if you want to try slowly reducing oz at the 2am feed in an attempt to move it to a bit later in the night - you may find if LO is ok with that that you never have to bother with PUPD anyway
Hope that is helpful x