Qlink Xp200 tire questions (Fat front)

I own a 09 Qlink XP200 with the 21" front tire. And ride on pavement 99% for the time. I noticed my front tire is wearing down and want to replace it but not with a stock size tire. And I'm having a hell of a time finding any info.
1. What is the biggest size front tire I can use with a stock size rear? ( I love the thick front tire look).
2. Since what I really want is 17" F/R supermoto wheels how can I accomplish this w/o spending a ton ?
Really any advice on getting tha

UPDATE: After a 2hr city nighttime cruise I stated to notice the ride felt extra bumpy. After a quick refill I stopped at the waterfront to grab a smoke before staring off again . That's when I noticed the (belts) peeking though the bald spots on my front tire. I need to know will this work a
SHINKO 705 90/90-21 (OEM is 2.75-21) work for the front tire
and for
the rear tie how bout a SHINKO 705 120/80-18 (OEM is 4.10-18) will these will fit my bike?
I think they will be fine but I need some real hand assurance that they will. I NEED TO KNOW ASAP I was lucky to make it home safely BUT NOW I CAN'T RIDE W/O A NEW TIRE!!! PLEASE for the love of the motorcycle saints someone help me! And thank you.t fat front tire look would be helpful. I don't have really any motorcycle tire experience I've all ways did custom cars & trucks never a motorcycle. Thanks in advance for any help .

Fat front tire makes it handle like $hit
I have a similar bike in China and doesn't corner well - slow to turn into a corner and needs forcing into it
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