Stroller and car seat troubles

Going to be a FTM in September and my husband and I are getting ourselves confused haha! We were thinking of getting a travel system but in Ohio the weight limit for car seats is 40 lbs and most of the travel system seats only go up to 30 or 35 lbs. Is there one that goes up to 40? Is it advisable to use one of these car seats regularly for fourish years? Maybe we should find a stroller that is compatible with a convertible car seat so we don’t have to buy multiple seats but we don’t know what to get! Basically, we want to purchase as few components as possible just for convenience (we do want two car seats though so we don’t always have to move one around between our cars or if family members are babysitting etc.). Any advice on making this purchase or product suggestions would really be appreciated!!