Ok, so I guess my only option is a 350W Sunlux Ultra or Retrolux...

Most of the retrofits I know available for the American MV ballasts, are 150W, 210W, 350W and 680W and 980W. There is no retrofit for 100W MV lamps.

Ballast can get comicated,  fue to impedance and the current u trying to push thhiugh it and the line  voltage.   

  Here in US u can see affect of choke ballast edp the 20 watt
Preheat chokes u  the Advance LC1420 for example  it will run a 14 watt to 22 watt lamps.     14  watt lamp have lowest arc voltage of 30-40 volt.   That lamp will work but ballast runsbit on hot side.   While U take sanw choke and 17 watt T8 2 footer
  That lamp 70 arc volt and lamp only need 270 mA.  Putting it on that choke balladt because of higher arc voltage the ballast rubs cooler whille  ballast is shoving 330 mA into the 270 mA 17 wat tube.   It forcing 22 watts of poeer into the lamp and ballast is running cooler than it ever did before.


   What I am saying  here U hace such a extreame low arc voltsge and high current lamps.   U have figure out how to take up 215 V out of 230 volt.   Yhe result will usually end up in Heat
  So let say have North american HPS choke.    Arc volt drop is 55 volt  but u have 120  volt.    If u add another ballast in series
 U can drop lamp aex vvolt down to 20 -25 volt  also  u can had caocitorrs in seriee to help fine tune the two balladt  to match the lamp requirement.   Thiing  is it need expermentijg bit also  montior the ballast Temp to not over heat them where u start burning the varnish off the chike windings

Thanks, do you know if there are any retrofit lamps what will fit a 100W MH ballast? I personally haven’t seen any of that wattage but I may be wrong

What's the point of streetlights Dayburning during Constructions? Just like this one:

https://maps.app.goo.gl/Eq4erF6Sxg4XjajG6?g_st=ac

Neon-argon filled HPS retrofit lamps, aren't suitable for CWA ballasts, as these ballasts can run them at very high currents, leading to very short lamp life, because of the lamps very high rate of lamp voltage rise during life, which isn't compliant to CWA ballasts.
If you want a HPS retrofit lamp for CWA ballast, you need a retrofit HPS lamp with a stable voltage through life like the Philips Retrolux or the EYE SunluxUltra, which are unsaturated HPS lamps that don't cycles at EOL but just glowing mercury color at EOL.

Sometimes technology can be complicated and it is always important to remember that when someone tries to correct you on a technical thing, to not take it as an attack on your person. (...)'s complicated when you're working with power factors, real and imaginary components of impedance and all that stuff. Hell, even the DC resistance of a choke can't always simply be ignored. Personally i still don't have a thorough understanding about why arc voltage has an effect on heat production in a series choke ballast, when the current is otherwise fine. 
It's staggering how something as simple as a choke in series with a tube is actually so complicated. I know i've shared wrong information before...

Anyway, i'm still toying with the idea of using a variac wired up as a choke to be an universal ballast for any and all tubes. As long as the inductance is large enough you should be able to set it to the value that makes you reach the exact lamp current (rms) you need.

I am interested in getting an HPS retrofit lamp because I don’t have any HPS ballasts in my (very limited) collection but still want to be able to see HPS light.

1: Efficiency

I can only assume that the efficiency of retrofit lamps is less than the “real thing”, is this true?

2: Compatibility

What brands are there? What types of ballasts are they compatible with?

3: Best choice for me

I have only 2 ballasts, one 100W HX pulse/probe start MH ballast and one 400W CWA probe start MH ballast. What do you think would be the best lamp option for me?

Thanks again for your help!

It gets really bothersome when different collectors share different conflicting opinions and try to correct me on them and being defensive of certain pieces of information that they share.

@WorldwideHIDCollectorUSA: Your Philips SI-51 two wires parallel ignitor never damaged by your ballasts, and this ignitor uses the ballast to make pulses, similar to a fluorescent starter.