Fall journey into menswear, advice most welcome.

[Casaubon]

As someone who finds much beauty in classic fall clothing, I'd like to weigh in with a few suggestions. Please take them with a grain of salt, as I would say I'm probably even less experienced than you.

1. My preference for a jacket color would also be brown, as I think it would be a tad easier to combine with trousers of any color you might want to wear in the season.
2. I own a jacket that was reduced in length from 38L to 38R, it was a risk but in the end I think it worked out. I can post photos if you'd like.
3. Regarding shoes, I'd personally opt for a pair of boots. I'm set on buying these next as soon as the opportunity arises, as I can't get over the fact how good the combination of suede and grained leather looks, especially paired with mid-gray flannel trousers, as shown here:

Grained Chocolate lace-up Boots Derby shoes - IRVING GOMME COUNTRY

Irving is a timeless Balmoral boot ! A bi-material stretch derby, very classy in the pure Bexley style.Blake welted with grained oily leather and padded collar, on rubber outsole, and tone on tone round waxed cotton laces guided by invisible eyelets and three brass hooks.A boot with a lot of...

www.bexley.com

However, I cannot fully attest to the quality of Bexley shoes, as I've only been wearing a pair of their Chelseas for a year now. The boots I linked to in particular are Blake welted with Dainite-like soles, good for rain. So if you are set on your criteria, then simply ignore the suggestion, as they are not Goodyear welted. I'm sure you can find better quality shoes in Canada, but I haven't seen this style anywhere else.
4. Also looking to boost my wardrobe with a pair of wool flannel trousers, I'd personally prefer a ligher grey, and I think you can safely complement that with a charcoal pair.
6. As far as denim is concerned, there is nothing I can add to what others already said, only agree.

 

[Panama]

Maybe I have been watching too much New Amsterdam, but I like my physicians in cardigans, sweater vests and cords...

What's a sleeveless cardigan called in North America? A waist coat thingy anyway....

 

[hamnjam]

As someone who finds much beauty in classic fall clothing, I'd like to weigh in with a few suggestions. Please take them with a grain of salt, as I would say I'm probably even less experienced than you.

1. My preference for a jacket color would also be brown, as I think it would be a tad easier to combine with trousers of any color you might want to wear in the season.
2. I own a jacket that was reduced in length from 38L to 38R, it was a risk but in the end I think it worked out. I can post photos if you'd like.
3. Regarding shoes, I'd personally opt for a pair of boots. I'm set on buying these next as soon as the opportunity arises, as I can't get over the fact how good the combination of suede and grained leather looks, especially paired with mid-gray flannel trousers, as shown here:

Grained Chocolate lace-up Boots Derby shoes - IRVING GOMME COUNTRY

Irving is a timeless Balmoral boot ! A bi-material stretch derby, very classy in the pure Bexley style.Blake welted with grained oily leather and padded collar, on rubber outsole, and tone on tone round waxed cotton laces guided by invisible eyelets and three brass hooks.A boot with a lot of...

www.bexley.com

However, I cannot fully attest to the quality of Bexley shoes, as I've only been wearing a pair of their Chelseas for a year now. The boots I linked to in particular are Blake welted with Dainite-like soles, good for rain. So if you are set on your criteria, then simply ignore the suggestion, as they are not Goodyear welted. I'm sure you can find better quality shoes in Canada, but I haven't seen this style anywhere else.
4. Also looking to boost my wardrobe with a pair of wool flannel trousers, I'd personally prefer a ligher grey, and I think you can safely complement that with a charcoal pair.
6. As far as denim is concerned, there is nothing I can add to what others already said, only agree.

your opinion is most welcome!

I'm planning a Brown Herringbone Tweed will be my first fall jacket as it seems so easy to pair with grey flannel. I'm becoming less drawn to a grey tweed jacket as a starter piece.
Agreed, with that a modest shortening can work but anything excessive will cause issues with proportions.
Boots may be a future consideration for next fall maybe? I ended up seeing an Allen Edmonds pebbled dark brown longwings on sale so made an impulse buy for my fall dress shoe. We'll see how it works out.
As boring as it sounds, I'm planning on light grey, medium grey flannel trousers to start. Thinking it will work well with the dark tweed jackets I have in mind.
denim and sports coats still seem like a strange pairing to me.

Maybe I have been watching too much New Amsterdam, but I like my physicians in cardigans, sweater vests and cords...

What's a sleeveless cardigan called in North America? A waist coat thingy anyway....

That's very similar to what I was thinking for the fall - cardigan, sweaters, vests layered under a sports coat. Are corduroys considered professional attire? I've always thought them to be akin to denim.