I use them to adjust my rate of lift, if I’m going into the corner and my kart is lifting the inside wheel high and fast then slamming down too quick chances are the front bar is too stiff.
Going to a softer bar for me allows the kart to pick up the wheel later in the corner for longer, and if the kart is sitting flat a stiffer bar will help it hike the inside up.
Just be careful a lift issue isn’t also the axle needing tuning.
And the sequel to TJ’s KP sticker quote has arrived. 
Assuming everything else is stock, and you’re running on decent tires (4 or fewer heat cycles just as an arbitrary number), then I would ask where you stack up relative to the front runners in your class. If you’re just lapping for fun then stop reading here.
If you’re more than let’s say 0.300” off the pace then you may be doing something wonky with your driving technique that causes you to favor an unorthodox setup. Driving matters most (insert the TJ sticker quote here), so if your technique is sound then I would forget what others are doing and continue to develop your setup for your driving. The front bar is a pretty influential piece on the OTK, and little changes can make a big difference, whether rotating the flat bar, or going to incrementally stiffer bars.
That said, I don’t have much experience driving recent OTK chassis, but those that I’ve hopped in have handled very well for me with the stock setup (bar in). They’re responsive to steering inputs, so I could see someone having problems if they’re too fast/sporadic with their hand movements. Smooth is fast.
Thanks Evan for pointing out some very specific things for me to keep an eye on as I chip away at my setup and/or driving challenges. (I’m a self-proclaimed “time trialist”, not a ‘fun karter’, but not racing tire to tire)
I possibly have never run tires with 4 or fewer heat cycles. Until now I’ve been satisfied to ‘estimate’ what I’d be turning as a lap time if I had newer tires. When I was farther from the pace this was arguably not a bad idea time and moneywise, but now that I’m getting close to the best times of the best drivers and really want to find out just where I sit pace-wise, I realize that I need to eliminate tires as a variable/doubt as well as provide myself a consistent kart to tune and drive against. To this end I have my first brand new set of tires mounted up.
Additionally, and not to bury the lede, but I just scaled my kart last night for the first time ever and discovered that my kart’s weight distribution is less than optimal (61.6% rear, 38.4% front). Which a) in retrospect seems remedial to just now be figuring out, and b) certainly opens up questions to the validity of any other tuning observations I’ve made (sigh).
So, I guess you could say that I’m in the hot-mess phase of trying to level-up, lol.
You’re in a fun phase, and one in which there are lots of learnings! The best thing you can do is to continue to 1) get tons of laps 2) experiment with setup changes noting the results and listening to the stop watch, and 3) get tons of laps.
New tires, as with anything in karting, is going to be a context-dependent change. In MOST circumstances you should expect to bolt them on and go faster; however, that may not always be the case, nor will it always be to the same degree. New tires and the effects they have on your lap times will depend on: what tire compound you’re using, track surface type (smooth, abrasive, etc.), track grip levels, and last but not least…driving technique.
I remember the first time I put on new tires for qualifying; it was at my first National race in Jacksonville in 2007. I had been using old rubber for all of the practice sessions, and was consistently 1.0-1.5 seconds off the top time. Threw on new tires for qualifying and holy shit did the kart come alive…qualified like P5 out of 50+ karts. Conversely, I’ve had plenty of instances where I’ve been very quick in practice on used tires, particularly in higher grip scenarios, and have gone the same time or slower when putting on new tires for qualifying.
It’s a certainty that things will be different when you bolt them on, but you may not know exactly HOW it will be different until you do so.
This makes me curious about your seat positioning.
@Muskabeatz you’re right - it is an extra fun time right now. Some proficiency, but still lots to discover and learn, and lots of possibilities seem open. The experiences you describe with new tires is intriguing. Gotta admit though, when I finally get to turn some laps with the stickers I feel like I damn well better be faster, or else it’s to the glue factory with me, hehe.
@CrocIndy Definitely, and that seat is no longer in the same position anymore - moved it this afternoon. 
Yeah, my kid is super tall and we don’t have numbers like that. Looks like the seat is very far back.
We moved ALL lead to the front. 5lbs lip of the seat, the 10lbs to pan behind the steering column, and in 10lbs front the the steering shaft. That put us at 43/56 with the LO206. Still need to re-weight and adjust for the KA.
Old post I know, but I suspect the side traction bar is a somewhat adjustable feature because the frame doesn’t have a flat section like most modern design frames. Your GP has the same curved frame rail as my older CRG.