Hi Cornishjock
Welcome to the forum.
I have a generation 1 auto Venga with the panny roof.
I also use roofbars with a roof box so feel qualified to comment.
My experience is:-
The auto is ridiculously thirsty for a modern car, especially around town.
Mainly because the engine is a Gamma series and has its roots back in 2007 but also because it has a torque converter auto which while generally reliable aren't the most efficient.
Low 20mpg's around town is normal, but you can crack 40mpg and more on a run if you aren't driving like Lewis Hamilton.
I've seen 45mpg on a run at around 60mph which for a gen1 is actually more than Kia reckon.
Cruise control helps the mpg on a run but I found my foot was better around town as cruise doesn't activate below 25mph.
Mine is a 4 speed but a 2019 will be the later 6 speed which is a little more efificent.
I can't comment on Bluetooth as yours will have a different head unit to mine ie: the 2 line red display you have in your old one.
And so lets talk about the panny roof and roofbars
It lightens the cabin enormously.
Depending where you park in winter it can promote condensation as it isn't a thermal roof.
The centre rubber seal can crack due to sun / heat and I had mine replaced under warranty. If it cracks and water can get through there is a gutter underneath which stops rain entering the cabin but do watch out for this although it shouldn't be a problem yet on a 2019.
It is important to grease it regularly with the correct grease. I'd imagine yours will be dealer serviced to keep the warranty so do check after every service they have cleaned and refreshed the grease (its white so is obvious).
We don't run with the roof open as it gets noisy due to the Venga's less than outstanding aerodynamics but we do like the light and airy feel it gives the cabin (and in fact we didn't realise it was an opening roof until we test drove ours so had no illusion about driving along with wind in our hair - Ok well maybe not me as I don't have much hair left)
As Uvox2 has shown, you need roof bars that grip the roof edge and pull up on the underneath of the door shuts.
I used
www.roofbox.co.uk and bought the Cruz Optiplus ST bars as I'm only an occasional roofbox user . Rroofbox.co.uk also do just foot packs so you may be able to find the right foot pack for your bars. For mine the footpack is CR5490. They do stock Thule so I imagine they will have the correct pack for your bars.
I've found that to get the correct tension on the bars, the feet will slightly indent on the doorshut area through the rubber pad supplied as part of the foot pack (although it doesn't break the paint). This isn't an issue for me as I keep cars until they die but if you are looking to resell its something to be aware of and a follow on buyer might ask why the weird indents.
To be honest unless you know what to look for an average buyer wouldn't notice but thought I'd mention it. And it does give a nice marker as to where to put the feet when you reinstall the bars
On no account open the panny roof when you have the bars on. When closed the roof is helping with the mechanical strength needed to allow the bars to tension correctly. If you move the roof when they are on, you alter that equation and body twist can happen / panny roof might not go back square etc. It also says this in the handbook. Dealers will reject any panny roof twisted warranty claims if they suspect you've opened the roof with bars on.
As you are a roof bar user already you know that getting things up and down requires some physical capability. I mention this because you will be loading above a pane of glass (albeit toughened) so you need to be sure you can physically cleanly lift things up and down. You will be looking at £500 or more for a broken sunroof panel with fitting. Also as an aside, the windscreen on these is not the same as the full roof model. If you ever need a windscreen from the replacing companies, they will always need to order it in as it isn't a stock item with any of them and last time I checked it was £700 or more. And like all glass, it will scratch if you drop sharp things on it.
Having said all that, we do like having the panny roof as it simply makes the cabin a nicer place to be with the increased light.
Pete