I've been rocking the BTR5 for a couple weeks now with both over-ears and IEMs. I too have the apple curse (sporting an iPhone 8, iPad Pro, and Mac). I haven't heard of the Qudelix 5k, have heard of the ES100 (it sounds pretty good). I've loved the BTR5 so much though that I just can't recommend anything else.
Yeah... iPhone sports the AAC which, in all honesty, isn't horrible. After reading various reviews and tech specs, I thought going in, "Well, this is going to suck". Plus, the BTR5 will be a significant upgrade from the little lightning to 3.5mm anyways. In terms of your laptop, it depends on the bluetooth technology in it. The BTR5 does have a USB-DAC function that supports extremely high bit-rates. For me, the BTR5 both satisfies having a portable option and a desktop option. That's primarily for its DAP function though.
As a quick note, I can confidently say that buying 2.5mm balanced cables is so worth it. Some of the audiophile recommendations you have to take with a grain of salt and ask yourself, "is it really going to make such a different that I need to spend more money?" When it comes to buying balanced cables, yes! In my experience, having a balanced cable not only provides more volume but better clarity and dynamics. I usually listen at 70 to 80 dBs so I don't care a whole lot in terms of power for volume. Oddly enough though, that additional power does add noticeably clarity to my music.
I'm not much farther along in my audiophile journey so I'm in a similar boat as you. I recently snatched a pair of Drop + Sennheiser HD6xx (which are, essentially, the same as HD650s but for half the price). They boast of a 300 ohm nominal impedance though. I spent probably hours researching if my little BTR5 could even power them. I don't have an amp stack unfortunately. Some say it would no problem. Some said it'd struggle. Some say it won't even come close. I can comment later if it works out.
All that to say, I was at crossroads where I knew I should probably put a little money into amp stack for at home use. I was looking at the Schiit Magni 3+ (amp) and Modi 3 (DAC) or the Topping A50 (DAC/amp combo). I just hated the thought of spending that money on equipment that was going to keep me anchored at my desk. Portability isn't necessarily a priority for me, but I also don't like to pay for something that doesn't offer a whole lot of versatility. So, I ended up gambling a little and got the Fiio M11 Pro which is a DAP that should, hopefully, still power all my over-ears and IEMs well. It ended up being more expensive for sure, but I see it as a worthwhile investment because it satisfies more of my needs. I can kick the iPhone out of the way when it comes to music, not relying on bluetooth. Larger storage. Awesome DAC and amp. Etc. Etc.
All of that to say... BTR5 is fantastic, highly recommend it. It'll be limited by the iPhone, but it's still a significant step up (trust me). Plus, you've got the USB-DAC function for your laptop. It terms of getting an amp stack, I guess it just depends on your personality and needs. Personally, I couldn't justify (in my mind) spending, potentially, $300 on what would be an entry-level stack that I would probably use 5% of the time. Getting the DAP, though more expensive, made sense because I'll be using that for hours everyday. So, if you're like "Man, I've got some power hungry cans that need a powerful amp" then, sure, go the amp stack route. But if you're just looking for something to power most IEM's and over-ears that can be used portably with your iPhone and through USB with your computer, then I definitely recommend going the BTR5 route.
