Is there any better methods than the ones im currently using?

If you don't want to change the structure of your code so that you continue using an infinite while loop, you can clean up a lot of the copied code by creating a function like this:

local function animateCooldown(tag, gui)
    if cs:HasTag(chr,tag) and not gui.Visible == true then
        gui.Visible = true
            gui.cd:TweenSize(UDim2.new(0,0,0,11),"In","Linear",6,true)
        delay(6, function()
        gui.Visible = false
                gui.cd:TweenSize(UDim2.new(0, 200,0, 11),"In","Linear",0.01,true)
        end)
    end
end

This would shorten your code to something like this:

while true do 
    animateCoolDown("BarrageCD", barragecd)
    animateCoolDown("ROLLCD", dashcd)

    if dashcd.Visible == true and barragecd.Visible == false then
        barragecd:TweenPosition(UDim2.new(0.93, 0,0.264, 0),"In","Linear",0.01,true)
        dashcd:TweenPosition(UDim2.new(0.93, 0,0.187, 0),"In","Linear",0.01,true)
    elseif dashcd.Visible == false and barragecd.Visible == true then
        dashcd:TweenPosition(UDim2.new(0.93, 0,0.264, 0),"In","Linear",0.01,true)
        barragecd:TweenPosition(UDim2.new(0.93, 0,0.187, 0),"In","Linear",0.01,true)
    elseif dashcd.Visible == false and barragecd.Visible == false then
        barragecd:TweenPosition(UDim2.new(0.93, 0,0.187, 0),"In","Linear",0.01,true)
        dashcd:TweenPosition(UDim2.new(0.93, 0,0.187, 0),"In","Linear",0.01,true)
    end
    wait()
end

However, instead of doing a giant loop, which is hard to update and is actually really inefficient sometimes, you should continue using CollectionService. However, you can use a function from the CollectionService called GetInstanceAddedSignal that will return a signal for you to connect a function to. It works similar to Instance:GetPropertyChangedSignal() if you've ever used that before.

-- this is the code you want to execute whenever a tag is added
local function onTagAddedToCharacter(character, tag, gui)
    if not gui.Visible then
        -- do all the animations
    end
end

-- since you're adding the tag to the character, we can get it here
CollectionService:GetInstanceAddedSignal("BarrageCD"):Connect(function(character)
    -- now we can call that function we just wrote
    onTagAddedToCharacter(character, "BarrageCD", barragecd)
end)

-- we can do the same thing but for a different tag
CollectionService:GetInstanceAddedSignal("ROLLCD"):Connect(function(character)
    -- now we can call that function we just wrote
    onTagAddedToCharacter(character, "ROLLCD", dashcd)
end)

I didn't write all of the code necessary to transition your current implementation to this, but I hope this gives you an idea of how to solve the problem :) You can shorten this, even more, to eliminate redundancy with a table of tags and for loops, but for now, this is a good place to start.