I've had 4x120W Kyocera
rigid panels since 2001, when they were $4/W.
In 2017 I added 4x120W flexible Hi-Power panels, mounted on top of my rigid bimini, using a brand recommended by a fellow cruiser. They were horrible
, never performing very well at all.
You may have your own reasons to go with flexible, but I'd strongly
recommend going with fixed panels if you possibly can. Not only will you get far more Watts for your dollar, they'll last longer as well.
Also, they do NOT need external frames. The frames they come with are VERY strong. My new panels are 1x2m monsters (400W & only $200 each in 2019). They're supported by my Targa-bar at the leading edge, but my davits
can only support them out at about the 1.15m point, meaning that .85m (33", or almost 3') is unsupported
except for their frames. Yet they're very strong, & have already survived Typhoon Rai/Odette in the Philippines
As for your question about putting them all in series or in 2P2S, I agree with Jammer & Mark: I'd recommend going 2P2S & saving the $$ a new MPPT would cost you. This assumes that there's no shading.
There's a very slight performance gain going 4S, because there's less wiring
losses, since the current is only half as much. Remember that wiring
losses are proportional to current squared, so lowering the current will lower your losses. But in this case, the losses would be minimal (if you use reasonable wire) so the savings would be minimal, & not worth the extra $$ for the new MPPT. That $$ would be much better spent on bigger panels.