You have two choices for vinyl replacement windows.
Insert windows for existing vinyl windows.
One solution that has been around for a while is the window insert an acrylic window that fits inside your existing windows often held in place with snap.
Necessary when existing window frames are old and deteriorating.
They will stop drafts dust air infiltration.
Just to get it out there you could use them but only after you remove the vinyl window completely and install them like it was new construction.
If they re rotten or badly out of square the whole unit including the frame may need replacing.
This is a much bigger and more complicated job than installing a vinyl window insert and may require a pro.
Replace the entire existing window down to the house frame.
Next measure the width at the top middle and bottom.
Add skylights to let in additional daylight.
If you need to stick to a tight budget you may want to look into vinyl windows.
More advanced project because you have to remove interior and exterior trims and sometimes the siding.
Keep the cold air out in the winter.
An insert window is a great option when you re happy with the size shape and operating style of your existing window.
Write down the measurements and use the smallest measurements for width and height to buy your new window.
Start by measuring inside the existing frame including the height in the middle and left and right sides.
Sliding windows slide open horizontally saving space while offering a clean modern design.
To do it that way would be a little counterproductive.
Energysavr window inserts are effective interior window insulation panels.
Fix it with a replacement window to seamlessly match the existing windows in your home.
Even relatively new vinyl windows less than ten years old can suffer from seal failures and degradation from exposure to weather and may need to be replaced.
The window insert to the rescue.
Your question if you can use replacement windows would be no.
Insert windows preserve the original frame exterior trim exterior siding and interior casing.
Push them into the opening inside your existing windows to create an insulating pocket of air.
The extrusions of the vinyl windows would not allow that.