Here are MY Z.5 STORAGE OPTIONS for PLANT OVERWINTERING:
1)-- Leave in situ planted in Glazed Pots, on Risers or pedestals (covered w/ plastic shrub covers)
2)--Open Screen Porch
3)- Bury Plastic Pots in Ground Trench
4)--Shed w/ small skylight, under Mature Hemlock
5)- Tiny Cellar 60 degrees , no windows
6)- Steps under Hurricane Door leading to Cellar Door
7)- South Facing House Plant Room w/wall of windows, skylights; open to living room, 65-70 degrees;
Filled w/ pots of Amaryllis, Xmas Cactus, Queen's Tears, Ferns , so window space is precious

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HOW SHOULD I STORE THESE PLANTS OVER WINTER:
(And Do They Need Water; how often?):
Pilea- Aluminum plant
Breynia- Snowbush
Pennesetum Villosum
Oxalis Cabernet
Dahlia ( can I leave planted in glazed pots and store in cellar?)
Taro ( can I leave planted in glazed pots? cellar or plant room? )
Colacasia ( """""" )
Alocasia ( """" )
Waterlilies
Clematis w/ tulips, allium, in glazed pots
Cissus Discolor
Begonia Rex (leave in soil in pots and let dry and go dormant in cellar?)
Tuberous Begonia (leave in soil in pots in cellar, let go dormant?)
Glazed or Plastic Pots Planted With Tulips,Hyacinthoides and Allium
Glazed or Plastic Pots Planted With Lilies , Allium, Tulips
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MY PAST/CURRENT SUCCESSFUL WINTER STORAGE METHODS:
Brugmansias -are stored in cellar, planted in glazed pots
Cannas -are stored in cellar,planted in plastic pots.
Abutilon - are transplanted into plastic pots in plant room
Ppl Wandering Jew- transplanted into plastic pots, in Plant Room
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The only other of your plants that I've overwintered are Dahlias and tuberous begonias. Last winter which was quite mild, the Dahlias stayed in pots in my unheated and sunny entryway. Both the pots and the Dahlias survived total benign neglect no water or attention all winter. I was surprised to see that they had survived, but I might suggest that a cool dryish indoor location like your cellar might do better. Someone wiser & more experienced than I should advise you about when to start watering and bringing them into the light.

My tuberous begonias go into a setting like your plant room (my east-facing cool kitchen windows.) They die back and I just tuck them under the bench holding other tender perennials until spring. I water them just enough so that they don't get overly dry, perhaps once a month a little bit. They start growing on their own when the time is right and I bring them up into the light then. Putting them outside on above freezing days might help them be less leggy - I am going to try that this spring with one of my pots.

Rex Begonia
Conditions: Considered perennials in tropical and semitropical climates, Rex begonias are frost tender and typically grown as annuals or houseplants in North America. They thrive in organic, sharp-draining soil and in shade with lots of humidity.
Care: Watering "on demand" (or when the soil is dry to the touch) is a great way to keep Rex begonias happy. Avoid soggy conditions, but do not allow plants to wilt. Give Rex begonias a diluted dose of organic, soluble food every four to six weeks during the growing season. Begonias do not grow or use fertilizer efficiently below 58F.
Overwintering: Rex begonias make excellent houseplants and can easily be overwintered indoors. To supply plants with adequate humidity, place containers on a tray of gravel, where runoff water may collect, evaporate, and raise the air-moisture level. Avoid placing plants near drafts.