Personally, I prefer parallel Christmas light sets because you can replace the bulbs with any type that you want as long as it does not overload the string. In addition, I do not have to worry about looking for missing bulbs or burned out bulbs in these sets. How about yourselves?

Im a bit torn on this. On one hand i love C7 lights because i have a lot more freedom with lamp chose but they get HOT! I also like mini lights because it is easier to set up but lamp choise is limited and repairing them can either be good fun or a chore for me.

The problem is, a parallel set on the mains require rather high power lamps, because it is very hard to make reasonably robust lamps for currents below 50mA. 20mA lamps are feasible, but become extremely fragile or inefficient.
So on 120V that means at least 6W lamps for the reasonable design, or 2.5W for the 20mA extreme. Both are quite high power, mainly for an indoor set.
A series running set may well use 3V lamps (40 lamp strings), so even when going to very convenient 0.5W per lamp, it means 150mA lamps, so about the same efficacy as an 18W 120V mains, plus way more robust short filament. So way more robust and more efficient lamps.
The drawback is, you then have to deal with the problems of a series running string (bypass elements, then fusing,...).
This is the reason, why all the indoor sets were mainly series strings and only the outdoor, where larger power bulbs were the choice, were made as parallel.

However you may use 12V feed and then use all lamps parallel, even with reasonably low power for an indoor set, yet benefit of the independent parallel operation. Plus less risk with isolation faults,...

The problem is, a parallel set on the mains require rather high power lamps, because it is very hard to make reasonably robust lamps for currents below 50mA. 20mA lamps are feasible, but become extremely fragile or inefficient.
So on 120V that means at least 6W lamps for the reasonable design, or 2.5W for the 20mA extreme. Both are quite high power, mainly for an indoor set.
A series running set may well use 3V lamps (40 lamp strings), so even when going to very convenient 0.5W per lamp, it means 150mA lamps, so about the same efficacy as an 18W 120V mains, plus way more robust short filament. So way more robust and more efficient lamps.
The drawback is, you then have to deal with the problems of a series running string (bypass elements, then fusing,...).
This is the reason, why all the indoor sets were mainly series strings and only the outdoor, where larger power bulbs were the choice, were made as parallel.

However you may use 12V feed and then use all lamps parallel, even with reasonably low power for an indoor set, yet benefit of the independent parallel operation. Plus less risk with isolation faults,...

There is such a thing as LED retrofit lamps for parallel strings.

There is such a thing as LED retrofit lamps for parallel strings.

That is only when you are happy with LEDs...

What about bigger Neon glow lamps ? Have those ever been used in common strings ? (I have so far only seen a picture in the gallery of a string from the ~40's with big spherical Neon lamps, but i think it was a rare thing)

Do modern Christmas light strings have toxic amounts of lead in them?

Do modern Christmas light strings have toxic amounts of lead in them?

Pretty much all the certified ones sold at retail stores will be in the safe range because all being sold at retail stores should be with the code in most countries, but if you buy from aliexpress or other less formal stores you are probably to get more lead content.

If there is lead there, it is embedded in the PVC of the wire insulation. (Well, there could also be lead in solder joints, but those are covered under insulation so not accessible)

If you swipe your hand on the wire, you might collect some (possibly invisible quantity) dirt from the surface of the wire onto your hand, which could contain lead

The wire by itself does not emit lead into the air or anything like that, except if it gets crumbling from age or UV exposure. In which case i guess it will just fall to the ground and mix into other dust and debris that is in there

I dont think it is realistic to reach to any "accountable", let alone dangerous, levels of lead in any of the mentioned ways though. The quanity released from the wire is tiny (if at all), and then there isn't a direct way in which any of it would reach to inside you anyway.. So just one of the things you shouldn't worry about