As far as the criminal clearances from the FBI and State: yes, your wife will need them if she lived in the States for more than six months. There is information at
this US2Canada link that tells you how to request, and expedite, those clearances. The FBI clearances can take as little as a month to get back if you follow their instructions for expediting the request. The State agencies all have their own requirements and timelines - but there is a contact list on the page. I'd suggest calling the applicable agencies and ask for specific info.
You can send the application without the clearances BUT if you do, you might end up with delays on the other end that would be longer than the delay caused by having to wait for the clearances before you submit the ap. That's because it takes about 6 weeks for CPC-Mississauga to send the application to London, and then a couple more weeks for London to log it in and do the initial assessment. At that point they'd fire off a letter to you requesting the clearances, if they weren't submitted upfront, and until you get that letter (with your file number) it's VERY risky to try to send the clearances to them. So, there you have a delay - and, in addition, visa offices will commonly apply a "bring forward date" to a file when they've had to request additional documents/information. What that means is that they'll write you and ask you to send them the clearances, and they'll allow you a certain number of days to get that info to them (normally about 90 days). And they put a 90 day "bf date" on your file - which means that, even if you send the requested info within a week, they're not going to pick up your file to see if you've submitted the requested information until those 90 days have passed. So, you can see, not submitting information "up front" can result in significant delays in processing. It's better to keep those "delays" on your end - and submit a complete application to benefit from the fastest processing possible.