I work for them.
Everything is the same as before, same manufacturers and suppliers, so nothing has changed in terms of quality you are used to (or lack of quality depending on which brand under Boohoo’s umbrella you buy 
).
However, by ‘quality’, bear in mind much of what you’re buying online isn’t brand new, it’s more often than not been worn and returned several times.
Our returns processors are on great pay rates but only because the job is so mindblowingly boring they can’t recruit unless there’s a pay incentive.
What this means, is that returns aren’t checked properly, and you’ll be wearing leotards (‘bodysuit’) generally worn without underwear, that’s already been worn, tight leggings , pyjamas, party frocks, bikinis, .... all worn.
Because of the pay later credit offered across the cheaper brands, people take advantage and buy tons of stuff, wear it on holiday, then return 9 out of 10 items several weeks later. ALL our returns from the cheap brands are like this.
Refunds are issued regardless of damage, no damage, no reason, whatever.
Sometimes a returns processor will do their job properly and sniff the armpits, check the crotch for goo, notice smoke or deodorant perfume smells, and on the few occasions I did Returns I did this, but once I opened packages with unmentionables in (clearly placed deliberately in the parcel by customers unhappy with their customer services experience so wanted to take it out on the Returns staff 
), after that I refused this task.
As for sizing, it isn’t generic across items and brands so hard to say.
You could try emailing customer services directly at the warehouse where the item is stocked (one of several nationwide with Boohoo), and if a member of staff has time, usually from HR (ask for the intern, give’s them something useful to do ) they can nip down with a tape measure and measure the item length. It’s not that hard, they just track it down on the shelf.
So as for sizing, ....Easier to just try it all before you (don’t) buy it all !