@ZZLOW 

If you happened to have M4 hardware V4, there should be configuration option to do that: How to select a preferred signal source on the Deco App

If not, see this document: Is the Signal Source for Satellite Decos Selectable on the Deco App?

You haven't told what are WiFi speeds you are getting from each Deco. Note that each hop will cut speed by half. Suppose, you are getting 600Mbps from Main Deco. In daisy chain configuration your Satellite #1 should deliver up to 300Mbps, Satellite #2 - under 150Mbps.

If you get better than 1/4 of Main Deco WiFi speed on Satellite #2, daisy chain won't deliver better results.

If your Deco mesh does not support preferred signal source selection, there are two options you could try:

1. Move Satellite #2 further away from Main. When it can't connect to Main Deco, it'll try to connect to Satellite #1.

2. Place Main Deco on First floor, with Satellites in the basement and second floor. To do that, you must have wired connection on First floor for Main Deco: either Ethernet cable or MoCA (Ethernet over the TV coax cable).

  @Alexandre. 

Thanks for the reply. Now, I get it a little bit more. 

Let say my current situation is assuming a 100mbps wifi on the main, on the satellite 2 I am getting around 20~30mbps only this is (likely?) caused by a 2 floor disparity. 

If I still want to maximize my speed on Satellite 2 without moving the main deco (unmovable) or chain it, just the natural way. 

Does it mean that I should get a better/stronger deco with bigger range coverage to help? 

Example 

M4 support up to 3800sqft

X60 support up to 5000sqft

X90 support up to 6000sqft

If I get the X60/90 will my speed improve gradually like lets say maybe at least hitting 75-80 mbps? 

  @ZZLOW 

If you are getting 100Mbps from Main Deco, your Satellite #2 shouldn't get more than 25-30 if you can daisy chain it. Which means, not different from what you have.

Buying more powerful Deco model could improve WiFi performance, but not dramatically. You may end up spending quite amount of money to get, perhaps, 40Mbps on Satellite #2, with the right Deco and setup. There is no guarantee, obviously.

If you still want to go that route, look for tri-band Deco units. These are even more expensive, but they can deliver a bit faster speeds on Satellites. Deco X90 is tri-band, so is Deco X68. Deco X60 is not.

For Internet speeds under 500Mbps, you may also consider tri-band Deco M9 Plus.

To get desired results, you'll have to replace all your M4s with different Decos. Meaning, just buying single X90 and adding it to your M4 set won't do much good. You should buy 2- or 3-pack X90 (or X68 or M9 Plus) and remove all M4s.

Take a look at your house and what else you can do to improve WiFi speeds, for less than replacing Deco hardware. It is recommended to have one Deco per floor, you already have that.

If you have TV cables going from the basement to other floors, they can be used to deliver Ethernet link and connect Decos to them. You might have other options depending on your house. For my house with three floors (basement, first, second) I used air vents to pass Ethernet cable from the basement to the first floor to connect Main Deco to. I also have central vacuum pipes I don't use, could have tried those. 

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>M4 support up to 3800sqft

Here is what does that marketing info mean. Take M4 to the place with absolutely no WiFi interference. Draw 3800 sq ft circle with M4 in its center. That circle will have radius of 34 ft.

It means WiFi signal from M4, albeit very weak, can reach up to 34 feet from M4, when there is absolutely no WiFi interference. The recommended distance from WiFi node to mobile devices connecting to that node, for real life cases, is much less.

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I recommend you read this FAQ: 

It is from ASUS, but principles of WiFi mesh and terminology used there are applicable to any other mesh, including Deco.