The simplified transit is in place so as noted just a review of your passport by immigration in a separate channel from those entering Canada, then into the International wing of the terminal, no security check or baggage claim/recheck. While there are two “swing gates” between the domestic and international wings of the terminal you cannot go into the domestic wing from the international through the same passage that permits domestic arriving passengers to pass through into the international wing without leaving airside or recreating security. You’d have to fully clear Canadian immigration and customs as if you were remaining in Canada, then re-enter through security the domestic wing. Not really worth it as the international MLL is much nicer. (if you have an Amex Platinum card or a Priority Pass there is also a Plaza Premium lounge in the international wing you can check out. Would not recommending you leave the terminal to venture either city centre Vancouver or Richmond.