I noticed that there's been no mention of flow rates. Nipple confusion is more likely to be nipple preference. Babies are smart; if a bottle is easier than the breast, they may begin to prefer the bottle and refuse the breast. Breastfeeding is active. Baby must suckle to trigger a letdown and must use mouth/tongue movements to promote milk flow. Bottle feeding, no matter what shape or material nipple, is passive. The milk flows no matter what and baby has to learn a new way of swallowing/breathing to avoid choking on the milk. It's a good idea to use "newborn" or "slow flow" or "stage 1" nipples, and there's no need to change the nipple type as baby gets older (after all, your breast doesn't change the way it lets milk down just because your baby is older). But every individual nipple is different, so it's a good idea to check each nipple. If you fill the bottle, just with water is fine, and hold it upside down, the milk should drip. . . drip. . . drip. . . relatively slowly. If it's drip.drip.drip or a stream, throw that nipple out. And you actually need to check each nipple, not just assume that since one from a particular brand was fine, others will be as well.
All the "when to start a bottle" recommendations are based on observations and preference of the suggesterthere's no science involved, and every baby will be different. If your baby is breastfeeding well, then it's probably not critical when to introduce the bottle (3 week, 4 weeks, whatever makes you feel comfortable). In general, breastfeeding is considered established at 6 weeks; at least, that's when your milk supply is typically established assuming no complications to beginning breastfeeding. It's often recommended to avoid introducing artificial nipples before that point because of the potential to impact the establishment of a good supply.
You don't have time to struggle with breastfeeding challenges, so really focus on getting breastfeeding off to a good start. If you're having ANY concerns or challenges, get help right away. Getting breastfeeding started right is more important than when to introduce a bottle or which bottle to use, IMO. It's a lot easier to "fix" bottle feeding after you return to work than to resolve any breastfeeding challenges when you've got to pump, bottle feed, and be separated from your baby for 1/3 of the time.