Been goin for 35 years...never did a fly in, don't think you need to unless you are just looking for excitement in the air.
If you are doing the opener, look for shallow lakes the warmer the better. I find I catch most fish in early season in water that is not over 6 or 8 feet deep. Long flat low lakes with slow moving water will warm particularly if it is stained with tanic acid...as the sun heats it up you can catch walleye all day long...but like always there are times you might as well go take a nap...cause they won't bite no-how.
Later in the year look for 55 degree water and forget about the shallows. Usually river mouth and rapid water from run off is good with some tangles and structure. That fishing is best in early morning and late afternoon...evening.
Be sure to have a shore lunch because of course you could eat a skunks butt you're so hungry, but nothing is as good as walleye out of cold water...in the spring. Watch out for old Mr tangle tooth...they like to hang around walleye beds and load those swaybellys up from a long winter of far and few meals.
Don't forget that in the colder lakes, lake trout are right up on top. You can long line Cleo's and William spoons and take a limit before noon.
As for limits...sheesh...when they get going you catch them one every cast, so limits are not an issue...save only the smaller fish as they taste the best.
If you go for a week, eventually they will "turn on" and then look out...a nice red and white or black and white can put a hundred fish in the boat...ah, well one at a time and back in the water, and your arm can get tired. Make sure to bend the barbs down so unhooking is easier and you don't injure any fish. After while, you will find that you don't have to keep any fish until just before you are leaving for lunch or back to the cabin.
Early season, Ontario DNR can be like the gastopo...putting up road blocks and searching your machine for anything and everything. So be sure to be ready for that...they like to write tickets to Americans...so they get your money in more ways than one. If you fool with bringing them home (and I never do that anymore) be sure to leave skin on the fillets so they can identify the fish and make sure you don't take over your limit or you can pay a healthy fine. Can't use the fuzz buster..up there and they do sit out in the middle of nowhere looking to nail your butt with that "funny license plate" even though Canadians can roar by and they won't turn a head.
Have fun...and make sure you take it safe because most places you will be the only boat on the lake. So take no chances...you don't want to be swimming in early water.
Oh, forgot one thing....buy some good charts/maps of the area, and try and get as far from roadside tourist trap places as possible. They get heavy use and the fish numbers can and do get depleted. Talk to a bait and tackle guy and tell them where you are going based upon some maps and then do the drive. 50 miles up and back will mean hungry fish with not a whole lot of knowledge about what artificial baits look like. That guy knows a hundred places and will get your started...and a good gps will finish the job.