125+ yr old home settled floors - LVF installation

[Andrew S.]

Good morning BP,

I'm looking for a sanity check on my installation flooring plan for my 125 yr old home.

The home is settled like many older homes are and historically had carpet throughout on top of the old hardwood floor. The hardwood floor is generally flat inside the rooms.  However the room transitions is where the old hardwood floor has some issues of a rise or fall (haven't taken a measurement of the exact rise or fall yet, guessing < 1/4" generally).  My plan to use LVF planks throughout the home (kitchen, living rooms, and bedrooms).  My plan is to hold onto the rental property for 2-5 years, house hack to rental. 

To deal with the changes in height that are in the transitions between rooms, I'm thinking about using various width boards to build custom height floor transition/ thresholds between each room.  I doubt I'll purchase the thresholds for the LVF planks due to price and lack in ability to customize the width and height changes necessary. 

As far as LVF selection goes, from my research a thinner (3.2 - 4 mm) LVF plank that will hopefully be more flexible to handle the not perfectly level hardwood floor underneath. 

Would an 8" wide handle the irregularities better than a 6" plank?

Would a plank with an underlayment handle it better (would increase thickness) ?

Would an underlayment I lay down myself be a better or worse option than the pre-installed underlayment or no underlayment and insulate the dropped ceiling below for noise reduction if needed?

Any experience with common brands and which have a strong locking mechanism?  Reading online reviews of Shaw, LifeProof, and Stainmaster all seem decent quality.

Anyone have experience with the planks below?  Or other LVF plank recommendations for a durable C class rental with not perfect even floor?

Lowes 3.2mm option: Shaw Matrix 14-Piece 5.9-in x 48-in Asheville Pine Locking Luxury Vinyl Plank

Lowes 4mm option: STAINMASTER 10-Piece 5.74-in x 47.74-in Washed Oak Dove Locking Luxury Vinyl Plank

Home Depot 7mm option with underlayment: LifeProof Sterling Oak 8.7 in. x 47.6 in. Luxury Vinyl Plank Flooring

My living room is above the lower unit in my duplex so I was considering a plank with an underlayment for sounds dampening for the living room, but if that increased thickness will handle the unevenness worse then I may look at other options.

There's a couple spots along the wall where the floor dips down as well.  Haven't figured out my game plan here yet.  I'm hesitant to pour a ton of self leveling compound due to added weight on the foundation may cause more settling damage. 

Thanks much!

Andrew