I have used Sav for a number of years, but never for .ca domain names.
Yes, you can list on their marketplace without using their landers. I do it all the time.
Yes the 4% commission applies whether one uses their landers or not.
I have bought and sold multiple domain names there, but never for a large amount, so not sure if the procedure to withdraw cash is different when the amount is large.
They have said it was coming for year(s), but as of now you can't use balance from sales directly for registrations, renewals, auction purchases, etc. That is you need to get paid out, and then pay as you go. They must needlessly pay a lot in PayPal, credit card, etc. fees.
I have never had any issues with registrations on the site, or with auction purchases or sales myself for that matter. With some extensions there seemed a long delay in names I transferred in appearing in my account (even though Whois showed they were at Sav). These problems were always resolved when I inquired, however. Customer service is not super fast, but always professional and helpful in my experience.
They use CloudFlare for setting DNS records. It is a little pause, and always need change one setting from default, and also does not work for a few extensions (probably ones that most do not own any domains in). But it is something to note re verification records. They suggest third party DNS services as a work around, and those do work.
You can list names for sale there that are registered anywhere, but if sold the transfer fee is added and the name gets transferred to Sav. I presume it only works for TLDs they handle, but never asked.
In their auctions, note that the name must be at least 60 days prior to expiry and all auctions start at $1. You can sometimes get deals at Sav on auctioned names, and sometimes end up selling for not much.
Sav have competitive rates on many extensions, and combined with being a member of both fast transfer networks, and the 4% commission, an attractive registrar and marketplace.
One fast transfer thing to note is they have no way to remove a name from fast transfer approval, other than to contact customer service. This is an issue and they really need to, like Dynadot, make it transparent to add or remove fast transfer approvals.
My experience has been positive with Sav. But I never tried anything with respect to a .ca there.
-Bob
PS I just saw the 21 day minimum to expiry for non-auction sales at Sav in post just above. Had not realized that. Good to know.