It should go okay and don't be nervous about it. The problem cases seem to be mostly when someone shows up at a land border with a truck with all of their items piled up on top like the Beverly Hillbillies and say they're 'moving' with complete disregard for fact Canada is a separate country (and no awareness they need some kind of document to move).
Main things I would suggest:
-do NOT travel with all your worldly goods. Normal luggage/items for a visit like you're planning (eg six months or so) will be fine.
-Tell the truth. Just emphasize the visit part. Have a copy of your PR app with you (even electronic) just in case.
-Ye, you have a spousal sponsorship app in process.
-You are coming for a visit. About six months. If your PR is approved while you're here, you may do the last paperwork in Canada. But the purpose of this visit is to visit and stay with your spouse _for a while._
-If not approved during your visit, you'll colour within the lines - you'll stay only as long as you're allowed to. (You can extend later if you want, don't get into that now).
-If you're asked about work or whatever - best to say no plans, you have savings, you're staying with your spouse so not much needed, you'd only work if you're allowed to.
-If it comes up whether you have a household in USA, try to make it clear you are travelling only with your personal items (consistent with a visit). You are NOT moving, you are visiting. (You'll have to fill in the rest of the blanks consistent with your actual situation). [My impression is that a more detailed discussion of eg having an apartment or house etc 'back home' may come up, but usually not if you're flying in.]
All these points are basically only a matter of emphasis - eg this is a visit not to stay indefinitely. (You can change your plans later if the circumstances change is the only difference there.)
I must ritually note that working for a company abroad CAN be permissible but it gets complicated if your'e working for a company with ANY direct links to Canada (like a Canadian office or working direclty on Canadian business etc). That's up to you to research. You can also apply for a work permit later - that's not a discussion to have at the border, you don't have any specific plans, and you wouldn't of course work in Canada until you have a status that would allow you to work legally.
[Granted most of the time border officers don't have any interest in people who have laptops and visit for a short while and do their regular work for abroad while they're in town. Just keep it simple regardless.]
