I love the essence of candles. Pillar candles are my choice but, I use jars for more scent. However, I must say diffusing oils are way more effective for the whole house and fast. Recently, I purchased a Honeywell humidifier with oil cup. It is simply awesome. I once worked for a large candle company. At least every month a fireman would come in and have to tell us candles are the number one cause of house fires. Believe me I can understand because I heard some crazy stories from customers and 99% were likely nothing to do with the candle but, the operator. You can't leave candles unattended and they are not meant to be liquified more than an inch. A half or fully liquified jar is a torch in your home! The company I worked for had scientists doing all kinds of experiments on how jars burn, burns with certain oils and wick length for types of oils and wax and so much more. I watched some of these experiments. You will never see me buy a homemade jar candle for this reason.
I have some elderly relatives who need to switch to oil diffusing. Just like a tea kettle without a whistle, they nod off and a candle is burning.
Read the ingredients and uses for the oils you choose. Some oils for instance are made to mix in wax or will say just for an oil burner which is different than a diffuser. I prefer oils that are safe enough for me to rub on my skin when diluted. I prefer natural and not synthetic because I am breathing this in.
If you have pets watch some of this Vet's videos. I once watched a DIY video where an untrained person put 10 drops of oil in a spray for her dog. This is so dangerous!
Dr. Becker-candles and plug ins: Dr. Becker Discusses the Dangers of Scented Candles and Plug-ins - YouTube