[woodcote]

I like the 1/24 size but also like the larger layout.
I guess it will come down to ghost cars/autonomous. Can you have those with Scalextric?

Scale...

If 1/24 is important to you, Scalextric is a non-starter. The track width is just too narrow. A compromise (although still a squeeze for the big cars) might be a larger 1/32 track system like the new Policar track. Distance between slots: Carrera 100mm; Policar 90mm Scalextric 78mm.

Ghost / autonomous cars.

All digital systems have autonomous cars - and a few traditional 'analogue' systems do too (although only one per lane). Carrera's ghost car is operated direct from the powerbase - no need for software or an app. Scalextric ARC Pro has a 'Pace Car' feature via the app. The Scalextric C7042 Advanced Power Base (APB) Pace Car is via the hardware, but there are also more sophisticated versions via a computer link-up. Slot.it's Oxigen system (which will also be the Policar digital system) is via the software, as is Scorpius Wireless. I believe the new SCX Advance system has a Pace Car feature via the app.

Almost all are a 'constant speed' pace car - so the top speed is limited by the slowest corner. In your space, that means your ghost cars will be slow down the long straights. If you tweak your pace cars - by putting stronger traction magnets in them, for example - they will be a little quicker on the straight and blisteringly fast around the corners. I'm not sure how realistic or satisfying that is?

One system that offer a much more sophisticated and realistic autonomous car feature is the Scalextric C7042 APB with a computer link up and running the RCS64 software. There are other software options for the APB with good ghost car features, but RCS64 is considered the best. This not an 'out-of-the-box' option and will require some hardware skills and a love of fiddling with computer programs.

Another system that offers more control over the ghost cars is Scorpius Wireless. This is a digital system that can be fitted to any track (plastic or wooden routed). It is expensive and requires a high level of skills to set up. A similar system is Slot.it Oxigen - although I'm not familiar with the details of the autonomous car feature.

Analogue / digital.

All cars running in digital mode need a digital chip (decoder) installed. If you are looking at running retro 1/32 and 1/24 cars from your youth, digital is not the best option. Scalextric offers both analogue and digital modes with its ARC Pro and C7042 APB systems. Carrera Digital does not - although DIY control units that switch between analogue and digital are very common in Carrera's key markets - North America and Central Europe. A Policar / Oxigen set-up with both digital and analogue capability would be relatively easy to set up. I don't believe SCX Advance offers an analogue option. An issue might be the motors in the older cars and their current-draw. The digital powerbases might not be able to handle them at all. That's where the Policar / Oxigen and Scorpius systems have a big advantage - the power to the track is your choice and the digital control is direct from the controller to the car's decoder. The SCX Advance system is similar, but less flexible out-of-the-box.

Recommendations.

There are plenty of considerations, but it does come down to budget. Given your desire to run 1/24 (and perhaps retro cars?) and an expectation to focus on racing autonomous cars...

If your budget is unlimited - get someone to build you a wood track for 1/24 and 1/32 cars and install Scorpius (or maybe Oxigen), with the option of analogue running too.

If your budget is limited and you want functionality out of the box - then it's Carrera (with someone converting the Control Unit to digital/analogue at some point). The Ghost Car feature is basic. The Carrera track could be converted at a later stage to run with the more complex (and expensive) Oxigen or Scorpius systems.

A compromise on scale, budget and need for some technical skills (software and hardware) is Policar track with Oxigen. Although the Policar track is getting very good reviews, the digital track pieces have yet to be released (expected 2021, I believe). In the meantime, Ninco lane changers and pit lanes can be used with Oxigen electronics installed.

Scalextric ARC Pro is the cheapest option, is good value, works out-of-the-box (via an app) and gives you that longer layout length that you liked - but you can't run 1/24 and the Pace Car feature is basic at best (Magic ARC app). The official Scalextric app Pace Car is very basic indeed.

Also dropping the 1/24, but having the best mid-budget ghost car feature is the Scalextric APB + RCS64 software.