I wouldn't worry too much about the adjustment period/difficulty. It's not like you have a lot of dives in a jacket. Diving is diving (breathe, swim around, surface, repeat). I think you will really like the snug fit/stability, bias to correct trim and modularity (ability to change wing capacities) the BPW affords. The BPW is designed to make good trim easier, but that also requires using the correct amount of weight correctly distributed.
Getting the harness adjusted properly for you/your wife may take a little while and it's best to get help in so doing. Find someone (if you can) who has dived a BPW for a long time to work with you. It's not hard, but the world is full of good idea fairies (including on SB) who don't know what they're talking about. A dive shop might be able to help, but it depends on whether the person working with you dives one (ask/never assume). A few pool sessions are always a good idea.
The proliferation of BPW designs means a lot of extraneous crap has been added to the original minimalist design. Things like chest straps, quick release ("QR") plastic buckles, cinches, danglies, bungies on wings, long inflator hoses (e.g. >22") and other contributions from the diving peanut gallery are just that. Simple/streamlined is better and often cheaper. Getting a well designed simple rig out of the box (including, but in no way not limited to DGX, HOG) is the best way to go. They're much cheaper (like half) than the XDeep NX, BTW. Be suspicious of "features." Less is more.
There are some differences from a jacket that will take getting used to: 1) the position of air cell in a wing is designed to trim you face down instead of feet down/head up. This will be most noticeable at the surface when the wing is fully inflated. You will need to lean back on the wing to keep upright. That might take you a few dives to get used to. 2) The waist strap/crotch strap means use of a standard weight belt gets tricky (e.g. weight belt over or under the crotch strap). You're diving in warm water (in the Phils) so the weight belt/ditchable weight issue is less critical than diving with a thick wetsuit or dry suit. As such, it's possible you can do away without ditchable weight altogether and mount weight on the cam strap. Alternatively, distribute weight in different places/use a combination of ditchable/non-ditchable weight to maintain proper center of gravity/trim. For example, a few pounds ditchable on the waist strap and a few pounds non-ditchable on the cam strap can give proper fore/aft trim and ability to dump weight without becoming a Polaris missle. Bottom line you should be able to hover motionless in a horizontal position indefinitely without having to fin, scull or other. If you can't, weight needs to be added/subtracted/shifted until you can. Any problem will be you/your weighting, not the rig.
XDeep for sure makes very good side mount gear, but I don't like the NX harness or wing sizing: plastic QR buckles, dangling straps and the wing size advertized (42 lbs) is too large for warm water/3 mm suits/aluminum 80 tanks. The harness is an example of corrupting a good simple design (continuous 2" webbing) with unnecessary "features" for the recreational tech wanna be market at a premium price. The wing size is more than enough for steel tanks using a drysuit if you intend to do that, as well. The amount of lift should be enough to offset the wetsuit compression/weight of gas in the full tank plus give you the ability to float head above the water, and no more. It should be enough to float a full tank rig at the surface. There are disadvantages to using a wing too big or too small. More lift isn't necessarily better. My suggested wing lift capacities are:
Warm water/3mm wet suit/aluminum tanks 20-25 lbs
Cold water/7 mm wet/dry suit/steel tanks 30-35 lbs
For reference, diving the Phils/Indonesia I use 4 lbs on the upper cam strap (no ditchable weight/AL80/ aluminum plate/3 mm suit). In that rig an 18 lbs wing is ample lift. I recommend you use a bit more weight/lift capacity starting out, but not much.
Modularity means that any wing (brand/size) will fit on any BP so you can mix brands. If it doesn't, find a different design/brand. Avoid anything brand specific/limited. It's either modular or it isn't. Flexibility is key. You can go with smaller wings as you gain experience, but work up to that.
Sorry if this is more than you wanted, but you asked.
Have fun in the Phils.
