Should my provisional be written as if it were a non-provisional?
A claim of your non-provisional application is entitled to the filing date of your provisional application if your provisional application adequately supports and enables the subject matter of the claim.
The reverse of this is that if your provisional does not adequately support and enable the subject matter of a claim, the claim is not entitled to the filing date of the provisional application.
For this reason, it is essential that your provisional application describes your invention is as much detail as you would describe it in a non-provisional application. If you fail to meet the "adequately support and enable" standard, it will be as if you never filed a provisional application.
Then why use a provisional application at all?
It entitles you to one more year of protection (since the 20 year term starts from the filing date of the non-provisional), and defers the filing and prosecution costs associated with the non-provisional.
While a provisional application does not have to meet the formality requirements of a non-provisional application, this is no benefit. This is because you would generally want your non-provisional application to be identical to your provisional application (though optionally omitting claims in the provisional), to avoid any doubt as to whether the claims of your non-provisional application are entitled to the filing date of your provisional application.
What if I'm in a hurry?
Get a patent attorney to do it for you. They know what they're doing, and can do it quickly if necessary.
But if that is not an option, you could quickly file a rough draft early, then file a second provisional shortly after which is more robust. You would then file a non-provisional (and any foreign applications) within 12 months of the first provisional, claiming the benefit of both.
The first provisional may or may not give you an earlier priority date, but it's at least arguable. But even if the first provisional is defective, the second one will at least save you (with only the cost of a few days or weeks of effective filing date).