The season is the whole planning problem
The Canadian Rockies run a short summer. Roughly June through September, with July and August as the reliable middle. Outside that, roads and lodges close, the lakes are frozen or still gray with silt, and a lot of what you came for is simply not available.
That compression is why Canada punishes late booking more than most destinations. The rooms at Lake Louise and in Banff townsite, and the good lodges along the Icefields Parkway, are a fixed and small supply against a fourteen-week window. A year ahead is normal here, not excessive.
Niagara and the east are the opposite. They work spring through fall, with autumn color through late September and October, and Niagara itself running year round.
Distances, honestly
The map lies about Canada more than anywhere except Australia.
Vancouver to Banff is a full day of driving through genuinely beautiful country, not a morning. Banff to Jasper along the Icefields Parkway is four hours if you never stop, and you will stop constantly, so give it a day. Toronto to Quebec City is around eight hours by road.
Do not try to combine the Rockies and the east in one trip unless you have three weeks or you are content to fly between them and lose two days to airports. They are further apart than London and Moscow.
Where I put people
The temptation in Banff is to book whatever is available and drive in each day. That works, and it costs you an hour each way in traffic that gets worse every year, plus a parking problem at the lakes that starts before sunrise in summer.
Staying in the townsite or at the lakes themselves costs more and buys back the two things that actually matter here: early mornings before the buses arrive, and evenings when everyone else has gone. On a trip this short and this seasonal, that is where I would rather your money went.
Things that catch people out
Moraine Lake is no longer a place you drive to. Private vehicle access has been restricted, so getting there means a shuttle or a tour booked in advance. People arrive expecting to park and find they cannot.
Parks passes are required and are easiest bought ahead rather than in line at the gate.
Wildlife is genuinely wild. Bears on the roadside are common and are not a photo opportunity to approach. Every lodge will tell you the same thing and some visitors still learn it the hard way.
Weather in the mountains ignores the calendar. Snow in June and heat in September both happen. Layers, always, and a real jacket even in midsummer.
Your phone plan probably does not cover Canada. It is a small thing that becomes a large one when you are navigating the Icefields Parkway with no signal and no downloaded map.