Biggest difference between a deck and porch besides the gaps in the deck floor is that the porch(no gaps) requires a slope to the floor. Since water can not pass between deck boards, it must be guided by a gradual slope away from the house to avoid puddles and the risk of standing water penetrating the house wall and rotting it. Any plan must start with a plan for adding this slope to the deck while maintaining structural integrity.

Surfacing is the easy part. Interlocking wood planks are common. Sheet materials are OK as long as they are rated for outside use. Be aware that vinyl has two key drawbacks in any outdoor settings:
1) all plastics expand and contract with temperature much more than wood/concrete/metal. This leads to a looser wavy surface on hot days and tightly stretching(and potentially overstretching on cold days. The darker the color, the hotter the plastic gets on sunny days and the worse this effect.
2) Sunlight degrades plastic softeners added to flexible plastics over time. Thus, the more sun exposure, the quicker the vinyl gets brittle and cracks.

Vinyl formulated for outdoor use, such as deck boards, is more resistant to such effects, but not totally immune.